Develop Reference

javascript min heap implementation for a storing a pair/tuple

I created a class to implement a min heap following a tutorial. It works fine for storing and retrieving integers. I want to store pairs in this class for example:
(5, 1)
(2, 4)
(6, 2)
The removeMin method should give (2, 4) back. Please find the class below:
class MinHeap {
constructor() {
this.storage = [];
this.size = 0;
}
getLeftChildIndex(index) {
return 2 * index + 1;
}
getRightChildIndex(index) {
return 2 * index + 2;
}
// check if this rounds down
getParentIndex(index) {
return Math.floor((index - 1) / 2)
}
hasLeftChild(index) {
return this.getLeftChildIndex(index) < this.size;
}
hasRightChild(index) {
return this.getRightChildIndex(index) < this.size;
}
hasParent(index) {
return this.getParentIndex(index) >= 0;
}
leftChild(index) {
return this.storage[this.getLeftChildIndex(index)];
}
rightChild(index) {
return this.storage[this.getRightChildIndex(index)];
}
parent(index) {
return this.storage[this.getParentIndex(index)];
}
isFull() {
return this.size == this.capacity;
}
swap(index1, index2) {
let temp = this.storage[index1];
this.storage[index1] = this.storage[index2];
this.storage[index2] = temp;
}
insert(data) {
this.storage[this.size] = data;
this.size += 1;
this.heapifyUp();
}
heapifyUp() {
let index = this.size - 1;
while (this.hasParent(index) &&
this.parent(index) > this.storage[index]) {
this.swap(this.getParentIndex(index), index);
index = this.getParentIndex(index);
}
}
removeMin() {
// if (this.size == 0)
// throw new Error("Empty Heap");
let data = this.storage[0];
this.storage[0] = this.storage[this.size - 1];
this.size -= 1;
this.heapifyDown();
return data;
}
heapifyDown() {
let index = 0;
while (this.hasLeftChild(index)) {
let smallerChildIndex = this.getLeftChildIndex(index);
if (this.hasRightChild(index) && this.rightChild(index) < this.leftChild(index))
smallerChildIndex = this.getRightChildIndex(index);
if (this.storage[index] < this.storage[smallerChildIndex])
break;
else
this.swap(index, smallerChildIndex);
index = smallerChildIndex;
}
}
getTop() {
return this.storage[0];
}
}
Could anyone please suggest changes to the above class to store and retrieve pairs.
Thanks

Assuming you want to sort your pairs by first element and then second, you would need to implement the comparison and swap operators for your int-pairs. You could store int-pairs as a 2-long array of int.

O(1) JavaScript Circular Buffer With GetMax and GetMin

So I've been scouring the web to find a way to do this but nothing I've found fits the exact solution we are looking for.
I have an app that stores float numbers in a circular buffer. The circular buffer class can be found here https://www.npmjs.com/package/circular-buffer.
In my app new numbers are coming in every few miliseconds and the buffer holds around 60K values.
For the purpose of this question though I created a circular buffer of 10 with a stream of 100 randomly generated numbers to simulate the incoming data. This is the line that generates the simulated stream:
for (let i = 0; i < valuesToEnqueueForDemoPurposes.length; i++) {
With my current setup, it is taking the cpu too much time to convert the circular buffer to an array and then calculate its min, max, min position / index number, max position / index number and standard deviations (but the stddev is not the focus of this question).
Here is my current code:
stats = require("stats-lite");
var CircularBuffer = require("circular-buffer");
var circularBuffer10 = new CircularBuffer(10);
var valuesToEnqueueForDemoPurposes = Array.from(Array(100)).map(x=>Math.random() * 1000)
for (let i = 0; i < valuesToEnqueueForDemoPurposes.length; i++) {
var newValue = valuesToEnqueueForDemoPurposes[i];
circularBuffer10.enq(newValue);
let valuesArray = circularBuffer10.toarray();
var maxIndex = valuesArray.reduce((iMax, x, i, arr) => x > arr[iMax] ? i : iMax, 0);
var minIndex = valuesArray.reduce((iMin, x, i, arr) => x < arr[iMin] ? i : iMin, 0);
var max = valuesArray[maxIndex];
var min = valuesArray[minIndex];
var standardDeviation = stats.stdev(valuesArray);
console.log(maxIndex);
console.log(max);
console.log(minIndex);
console.log(min);
console.log(standardDeviation + "\n\n");
}
So I was wondering if it was possible to optimize this code with different data structures.
The closest answer I've found to solve this issue is from this SO answer: https://stackoverflow.com/a/48610455
It uses:
a queue of N items
a Min / Max Heap to track the min / max item.
A hash map to track the frequency of each item.
But the problem with this solution is that the heap is always growing and with the amount of differing incoming data I receive, this would cause a serious problem. And it also only calculates the maximum.
Also found this c++ solution but it is only for a normal queue, a max (not min) and I wasn't able to reproduce in javascript:
https://www.geeksforgeeks.org/design-a-queue-data-structure-to-get-minimum-or-maximum-in-o1-time/
Does anyone know if it would be possible, using whatever combination of data structures, to find the Max or Min in O(1) for this type of scenario (with or without circular buffers)?

Thanks to #thomas's advice I was able to alter the circular buffer class I was using so that the sum, mean,max, min and standard deviations are calculated on average at O(1) but at the worst O(N). Worked like a charm for the performance I needed.
Please note that for my purposes I have only altered the "unshift" method of the CBuffer circular buffer class . So the other methods won't be updating the max, min and standard deviations correctly. Here is the link to the jsfiddle:
https://jsfiddle.net/29f4an7s/
And here is my testing code:
// A standard deviation object constructor. Running deviation (avoid growing arrays) which
// is round-off error resistant. Based on an algorithm found in a Knuth book.
class StandardDeviation {
constructor() {
this.v = 0;
this.w = 0;
this.S = 0;
this.count = 0;
}
// Add a measurement. Also calculates updates to stepwise parameters which are later used
// to determine sigma.
add(measurement) {
this.count += 1;
this.w = this.v;
this.v = this.v + (measurement - this.v) / this.count;
this.S = this.S + (measurement - this.w) * (measurement - this.v);
}
// Performs the final step needed to get the standard deviation and returns it.
get() {
if (this.count < 2) {
// There are less measurements accumulated than necessary to perform computation
return 0.0;
} else {
return Math.sqrt(this.S / (this.count));
}
}
// Replaces the value x currently present in this sample with the
// new value y. In a sliding window, x is the value that
// drops out and y is the new value entering the window. The sample
// count remains constant with this operation.
replace(x, y) {
const deltaYX = y - x;
const deltaX = x - this.v;
const deltaY = y - this.v;
this.v = this.v + deltaYX / this.count;
const deltaYp = y - this.v;
const countMinus1 = this.count - 1;
this.S = this.S - this.count / countMinus1 * (deltaX * deltaX - deltaY * deltaYp) - deltaYX * deltaYp / countMinus1;
}
// Remove a measurement. Also calculates updates to stepwise parameters which are later used
// to determine sigma.
remove(x) {
this.w = (this.count * this.v - x) / (this.count - 1);
this.S -= (x - this.v) * (x - this.w);
this.v = this.w;
this.count -= 1;
}
}
function CBuffer() {
// handle cases where "new" keyword wasn't used
if (!(this instanceof CBuffer)) {
// multiple conditions need to be checked to properly emulate Array
if (arguments.length > 1 || typeof arguments[0] !== 'number') {
return CBuffer.apply(new CBuffer(arguments.length), arguments);
} else {
return new CBuffer(arguments[0]);
}
}
// if no arguments, then nothing needs to be set
if (arguments.length === 0)
throw new Error('Missing Argument: You must pass a valid buffer size');
// this is the same in either scenario
this.length = this.start = 0;
// set to callback fn if data is about to be overwritten
this.overflow = null;
// set to callback fn if data is about to be overwritten
this.maxIndex = null;
this.minIndex = null;
this.max = null;
this.min = null;
this.sum = null;
this.mean = null;
this.standardDeviation = new StandardDeviation();
// emulate Array based on passed arguments
if (arguments.length > 1 || typeof arguments[0] !== 'number') {
this.data = new Array(arguments.length);
this.end = (this.size = arguments.length) - 1;
this.push.apply(this, arguments);
} else {
this.data = new Array(arguments[0]);
this.end = (this.size = arguments[0]) - 1;
}
// need to `return this` so `return CBuffer.apply` works
return this;
}
function defaultComparitor(a, b) {
return a == b ? 0 : a > b ? 1 : -1;
}
function mod(n, m) {
return ((n % m) + m) % m;
}
CBuffer.prototype = {
// properly set constructor
constructor : CBuffer,
/* mutator methods */
// pop last item
pop : function () {
var item;
if (this.length === 0) return;
item = this.data[this.end];
// remove the reference to the object so it can be garbage collected
delete this.data[this.end];
this.end = (this.end - 1 + this.size) % this.size;
this.length--;
return item;
},
// push item to the end
push : function () {
var i = 0;
var returnOverflow = false;
// check if overflow is set, and if data is about to be overwritten
if (this.overflow && this.length + arguments.length > this.size) {
// call overflow function and send data that's about to be overwritten
for (; i < this.length + arguments.length - this.size; i++) {
returnOverflow = this.data[(this.end + i + 1) % this.size];
// this.overflow(this.data[(this.end + i + 1) % this.size], this);
}
}
// push items to the end, wrapping and erasing existing items
// using arguments variable directly to reduce gc footprint
for (i = 0; i < arguments.length; i++) {
this.data[(this.end + i + 1) % this.size] = arguments[i];
}
// recalculate length
if (this.length < this.size) {
if (this.length + i > this.size) this.length = this.size;
else this.length += i;
}
// recalculate end
this.end = (this.end + i) % this.size;
// recalculate start
this.start = (this.size + this.end - this.length + 1) % this.size;
// return number current number of items in CBuffer
return returnOverflow;
},
// reverse order of the buffer
reverse : function () {
var i = 0,
tmp;
for (; i < ~~(this.length / 2); i++) {
tmp = this.data[(this.start + i) % this.size];
this.data[(this.start + i) % this.size] = this.data[(this.start + (this.length - i - 1)) % this.size];
this.data[(this.start + (this.length - i - 1)) % this.size] = tmp;
}
return this;
},
// rotate buffer to the left by cntr, or by 1
rotateLeft : function (cntr) {
if (typeof cntr === 'undefined') cntr = 1;
if (typeof cntr !== 'number') throw new Error("Argument must be a number");
while (--cntr >= 0) {
this.push(this.shift());
}
return this;
},
// rotate buffer to the right by cntr, or by 1
rotateRight : function (cntr) {
if (typeof cntr === 'undefined') cntr = 1;
if (typeof cntr !== 'number') throw new Error("Argument must be a number");
while (--cntr >= 0) {
this.unshift(this.pop());
}
return this;
},
// remove and return first item
shift : function () {
var item;
// check if there are any items in CBuff
if (this.length === 0) return;
// store first item for return
item = this.data[this.start];
// recalculate start of CBuffer
this.start = (this.start + 1) % this.size;
// decrement length
this.length--;
return item;
},
// sort items
sort : function (fn) {
this.data.sort(fn || defaultComparitor);
this.start = 0;
this.end = this.length - 1;
return this;
},
// add item to beginning of buffer
unshift : function () {
var i = 0;
var returnOverflow = false;
if (this.length == this.size) {
returnOverflow = this.last();
}
for (i = 0; i < arguments.length; i++) {
this.data[(this.size + this.start - (i % this.size) - 1) % this.size] = arguments[i];
}
if (this.size - this.length - i < 0) {
this.end += this.size - this.length - i;
if (this.end < 0) this.end = this.size + (this.end % this.size);
}
if (this.length < this.size) {
if (this.length + i > this.size) this.length = this.size;
else this.length += i;
}
this.start -= arguments.length;
if (this.start < 0) this.start = this.size + (this.start % this.size);
this.recalculateMaxMin(arguments[0], returnOverflow);
this.sum += arguments[0];
if (returnOverflow) {
this.sum -= returnOverflow;
this.standardDeviation.replace(returnOverflow, arguments[0])
}
else {
this.standardDeviation.add(arguments[0]);
}
this.mean = this.sum / this.length;
return returnOverflow;
},
/* accessor methods */
// return index of first matched element
indexOf : function (arg, idx) {
if (!idx) idx = 0;
for (; idx < this.length; idx++) {
if (this.data[(this.start + idx) % this.size] === arg) return idx;
}
return -1;
},
// return last index of the first match
lastIndexOf : function (arg, idx) {
if (!idx) idx = this.length - 1;
for (; idx >= 0; idx--) {
if (this.data[(this.start + idx) % this.size] === arg) return idx;
}
return -1;
},
// return the index an item would be inserted to if this
// is a sorted circular buffer
sortedIndex : function(value, comparitor, context) {
comparitor = comparitor || defaultComparitor;
var isFull = this.length === this.size,
low = this.start,
high = isFull ? this.length - 1 : this.length;
// Tricky part is finding if its before or after the pivot
// we can get this info by checking if the target is less than
// the last item. After that it's just a typical binary search.
if (low && comparitor.call(context, value, this.data[high]) > 0) {
low = 0, high = this.end;
}
while (low < high) {
var mid = (low + high) >>> 1;
if (comparitor.call(context, value, this.data[mid]) > 0) low = mid + 1;
else high = mid;
}
return !isFull ? low :
// http://stackoverflow.com/a/18618273/1517919
(((low - this.start) % this.length) + this.length) % this.length;
},
/* iteration methods */
// check every item in the array against a test
every : function (callback, context) {
var i = 0;
for (; i < this.length; i++) {
if (!callback.call(context, this.data[(this.start + i) % this.size], i, this))
return false;
}
return true;
},
// loop through each item in buffer
// TODO: figure out how to emulate Array use better
forEach : function (callback, context) {
var i = 0;
for (; i < this.length; i++) {
callback.call(context, this.data[(this.start + i) % this.size], i, this);
}
},
// construct new CBuffer of same length, apply map function, and return new CBuffer
map : function (callback, context) {
var outCBuffer = new CBuffer(this.size);
for (var i = 0; i < this.length; i++) {
var n = (this.start + i) % this.size;
outCBuffer.push(callback.call(context, this.data[n], i, this));
}
return outCBuffer;
},
// check items agains test until one returns true
// TODO: figure out how to emulate Array use better
some : function (callback, context) {
var i = 0;
for (; i < this.length; i++) {
if (callback.call(context, this.data[(this.start + i) % this.size], i, this))
return true;
}
return false;
},
// calculate the average value of a circular buffer
avg : function () {
return this.length == 0 ? 0 : (this.sum() / this.length);
},
// loop through each item in buffer and calculate sum
sum : function () {
var index = this.length;
var s = 0;
while (index--) s += this.data[index];
return s;
},
// loop through each item in buffer and calculate sum
getMaxPosition : function () {
// return 0
return (this.start + this.start + this.maxIndex) % this.size;
},
// loop through each item in buffer and calculate sum
getStandardDeviation : function () {
// return 0
return this.standardDeviation.get();
},
// loop through each item in buffer and calculate sum
getMinPosition : function () {
// return 0
return (this.start + this.start + this.minIndex) % this.size;
},
recalculateMaxMin : function (newValue, returnOverflow) {
if (this.length == 1) {
this.max = newValue;
this.maxIndex = this.start;
this.min = newValue;
this.minIndex = this.start;
return;
}
// Max / Mins
if (newValue > this.max) {
this.max = newValue;
this.maxIndex = this.start;
}
if (newValue < this.min) {
this.min = newValue;
this.minIndex = this.start;
}
// If overflow max or min recalculate
if (
returnOverflow && (returnOverflow >= this.max || returnOverflow <= this.min)
) {
this.maxIndex = 0;
this.minIndex = 0;
this.max = this.data[0];
this.min = this.data[0];
for (let i = 0; i < this.length; i++) {
if (this.data[i] > this.max) {
this.maxIndex = i;
this.max = this.data[i];
}
if (this.data[i] < this.min) {
this.minIndex = i;
this.min = this.data[i];
}
}
}
},
// loop through each item in buffer and calculate median
median : function () {
if (this.length === 0)
return 0;
var values = this.slice().sort(defaultComparitor);
var half = Math.floor(values.length / 2);
if(values.length % 2)
return values[half];
else
return (values[half-1] + values[half]) / 2.0;
},
/* utility methods */
// reset pointers to buffer with zero items
// note: this will not remove values in cbuffer, so if for security values
// need to be overwritten, run `.fill(null).empty()`
empty : function () {
var i = 0;
this.length = this.start = 0;
this.end = this.size - 1;
return this;
},
// fill all places with passed value or function
fill : function (arg) {
var i = 0;
if (typeof arg === 'function') {
while(this.data[i] = arg(), ++i < this.size);
} else {
while(this.data[i] = arg, ++i < this.size);
}
// reposition start/end
this.start = 0;
this.end = this.size - 1;
this.length = this.size;
return this;
},
// return first item in buffer
first : function () {
return this.data[this.start];
},
// return last item in buffer
last : function () {
return this.data[this.end];
},
// return specific index in buffer
get : function (arg) {
return this.data[mod(this.start + arg, this.size)];
},
isFull : function (arg) {
return this.size === this.length;
},
// set value at specified index
set : function (idx, arg) {
return this.data[(this.start + idx) % this.size] = arg;
},
// return clean array of values
toArray : function () {
return this.slice();
},
// return a string based on the array
join : function(separator) {
if (!separator) separator = ',';
var outString = new String(this.data[0]);
for (var i = 1; i < this.length; i++) {
var n = (this.start + i) % this.size;
outString = outString.concat(separator, this.data[i]);
}
return outString;
},
// slice the buffer to an arraay
slice : function (start, end) {
var size = this.length;
start = +start || 0;
if (start < 0) {
if (start >= end)
return [];
start = (-start > size) ? 0 : size + start;
}
if (end == null || end > size)
end = size;
else if (end < 0)
end += size;
else
end = +end || 0;
size = start < end ? end - start : 0;
var result = Array(size);
for (var index = 0; index < size; index++) {
result[index] = this.data[(this.start + start + index) % this.size];
}
return result;
}
};
var bufferLength = 3;
var numbersToGenerate = 10;
var circularBufferN = new CBuffer(bufferLength);
var valuesToEnqueueForDemoPurposes = Array.from(Array(numbersToGenerate)).map(x=>Math.random() * 1000)
for (let i = 0; i < valuesToEnqueueForDemoPurposes.length; i++) {
var newValue = valuesToEnqueueForDemoPurposes[i];
console.log("\n\nNEW VALUE****************************************************************:");
console.log(newValue);
console.log("STARTING UNSHIFT:");
console.log(circularBufferN.unshift(newValue));
let valuesArray = circularBufferN.data;
var maxIndex = circularBufferN.maxIndex;
var minIndex = circularBufferN.minIndex;
var max = valuesArray[maxIndex];
var min = valuesArray[minIndex];
console.log("Max Index");
console.log(maxIndex);
console.log("Max:");
console.log(max);
console.log("Min Index:");
console.log(minIndex);
console.log("Min:");
console.log(min);
console.log("Start:");
console.log(circularBufferN.start);
console.log("ORDERED ARRAY:");
console.log(circularBufferN.toArray());
console.log("Max Position:");
console.log(circularBufferN.getMaxPosition());
console.log("Min Position:");
console.log(circularBufferN.getMinPosition());
console.log('Sum:');
console.log(circularBufferN.sum);
console.log("mean:");
console.log(circularBufferN.mean);
console.log("Derived Standard Deviation");
console.log(circularBufferN.getStandardDeviation());
}

Subset sum with number reuse allowed

I have a list of positive integers e.g. 15, 29, 110, and a target e.g. 44. I'm trying to find all possible combinations which sum to the target but importantly, the numbers in the set can be used multiple times e.g.
Target = 44
Result = 1x15, 1x29
Target = 307
Result = 2x110, 3x29
I found a dynamic programming solution which works when the combination is no more than one of each number. So Target 44 works but not my 307 example (returns Not Found).
How can the multiples or number reuse be done?
function subset(people, min, max)
{
var subsets = [];
subsets[0] = '';
for (var person in people)
{
for (var s = min-1; s >= 0; --s)
{
if (s in subsets)
{
var sum = s + people[person];
if (!(sum in subsets))
{
subsets[sum] = subsets[s] + ' ' + person;
if (sum >= min && sum <= max)
{
return subsets[sum];
}
}
}
}
}
return 'Not found';
}
var p = {
optionA:15,
optionB:29,
optionC:110
};
var qty = 307;
console.log(subset(p, qty, qty));

Try this recursive solution:
function subset(people, min, max) {
const pairs = Object.entries(people),
results = [],
getSum = multiplications => multiplications.reduce((sum, multiplicator, position) =>
sum + pairs[position][1] * multiplicator, 0),
formatResult = result => result.map(multiplications =>
multiplications.reduce((res, multiplicator, position) =>
(multiplicator > 0 ? res.push(`${multiplicator}x${pairs[position][1]}`) :
res, res), []));
function findSums(multiplications, position) {
let s;
while((s = getSum(multiplications)) <= max) {
if (s >= min) {
results.push([...multiplications]);
}
if (position < pairs.length - 1) {
const m = [...multiplications],
nextPosition = position + 1;
m[nextPosition]++;
findSums(m, nextPosition);
}
multiplications[position]++;
}
}
findSums(pairs.map(_ => 0), 0);
return results.length > 0 ? formatResult(results) : "Not found";
}
var p = {
optionA:15,
optionB:29,
optionC:110
};
var qty = 307;
console.log(subset(p, qty, qty));

Change the second loop in such way:
for (var s = 0; s <= wantedSum - people[person] ; s++)
Using this approach you fill all entries of subsets[] array\list where index is multiple of people[person] (instead of single entry). For example, with value 3 you fill 3,6,9,12... entries.

returning equation with all possible parenthesis combinations and the result of each

On a recent interview, I was asked to return all possible combinations of order of operations on an input string, and the result. you should return all the ways/combinations in which you can "force" operations with parenthesis. I got the result (right hand side of the equation) but got stuck on the left side. how could I have done the left side and the right hand side together? Seems like two problems in one...
//input:
console.log(diffWaysToCompute("2 * 3 - 4 * 5"));
//output:
(2*(3-(4*5))) = -34
((2*3)-(4*5)) = -14
((2*(3-4))*5) = -10
(2*((3-4)*5)) = -10
(((2*3)-4)*5) = 10
'use strict'
function getNumbersAndOperators(str) {
var arr = str.split(" ");
var operators = [];
for (var i = 0; i < arr.length; i++) {
if (arr[i] === "-" || arr[i] === "*" || arr[i] === "+") {
operators.push(arr[i]);
arr.splice(i, 1);
// console.log(operators);
}
}
return [arr, operators];
}
// console.log(getNumbersAndOperators("2 - 1 - 1"))
var diffWaysToCompute = function (input) {
// var numbers = input.split(" ");
// console.log(numbers);
// // console.log(number);
var results = compute(input);
results.sort(function (a, b) {
return a - b;
});
//put the numbers length into valid parenthesis:
var NumbersAndOperators = getNumbersAndOperators(input);
var numbers = NumbersAndOperators[0];
console.log(numbers);
var operators = NumbersAndOperators[1];
console.log(operators);
var parens = validParentheses(numbers.length);
// console.log(numbers);
console.log(operators);
// for (var i = 0; i < parens.length; i++) {
// for (var j = 0; j < parens[i].length; j++) {
// var val = parens[i][j];
// console.log(val);
// if (val === " ") {
// var num = numbers.shift();
// parens.splice(val, 0, num);
// //starting running into infinite loops and out of time.
// j--;
// }
// }
// i--;
// }
console.log(parens);
return results;
};
function validParentheses(n) {
if (n === 1) {
return ['( )'];
}
var prevParentheses = validParentheses(n - 1);
var list = {};
prevParentheses.forEach(function (item) {
list['( ' + item + ' )'] = null;
list['( )' + item] = null;
list[item + '( )'] = null;
});
console.log(Object.keys(list))
return Object.keys(list);
}
function compute(str) {
var res = [];
var i;
var j;
var k;
var left;
var right;
var string = [];
var placed = true;
if (!/[+*-]/.test(str)) { // + - *
return [parseInt(str)];
}
for (i = 0; i < str.length; i++) {
if (/\+|\-|\*/.test(str[i])) { // + - *
left = compute(str.substring(0, i));
right = compute(str.substring(i + 1, str.length));
for (j = 0; j < left.length; j++) {
for (k = 0; k < right.length; k++) {
if (str[i] === '+') {
res.push(parseInt(left[j] + right[k]));
} else if (str[i] === '-') {
// string.push("(" + str[i-2], str[i+2] + ")");
res.push(parseInt(left[j] - right[k]));
} else if (str[i] === '*') {
res.push(parseInt(left[j] * right[k]));
}
}
}
}
}
// console.log(string);
return res;
}
console.log(diffWaysToCompute("2 - 1 - 1"));
console.log(diffWaysToCompute("2 * 3 - 4 * 5"));

I never had to do such silly things, so let me try my teeth at it now.
(Caveat as always: it's highly simplified and without any checks&balances!)
The parser is the simplest thing here:
/*
Use of strings instead of ASCII codes for legibility.
I changed x - y to x + (-y) not only for convenience
but for algebraic correctness, too.
#param a array number nodes
#param o array operator nodes
*/
function parse(s,a,o){
var fnum = 0;
var uminus = false
for(var i=0;i<s.length;i++){
switch(s[i]){
case '-': uminus = true;
a.push(fnum);
o.push('+');
fnum = 0;
break;
case '+':
case '*':
case '/': if(uminus){
uminus = false;
fnum *= -1;
}
a.push(fnum);
o.push(s[i]);
fnum = 0;
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9': fnum = fnum * 10 + parseInt(s[i]);
break;
default: break;
}
}
//assuming symmetry
a.push(fnum);
}
The (-generation took me some time, too much time--I cheated here ;-)
/*
Found in an old notebook (ported from C)
Algo. is O(n^2) and can be done faster but I
couldn't be a...ehm, had no time, sorry.
#idx int index into individual result
#n int number of groups
#open int number of opening parentheses
#close int number of closing parentheses
#a array individual result
#all array space for all results
*/
function makeParens(idx,n,open,close,a,all){
if(close == n){
all.push(a.slice(0));
return;
} else {
if(open > close){
a[idx] = ')';
makeParens(idx+1,n,open,close+1,a,all);
}
if(open < n){
a[idx] = '(';
makeParens(idx+1,n,open+1,close,a,all);
}
}
}
And now? Yepp, that took me a while:
/*
The interesting part
Not very optimized but working
#s string the equation
#return array nicely formatted result
*/
function parenthesing(s){
var nums = [];
var ops = [];
var all = [];
var parens = [];
// parse input into numbers and operators
parse(input,nums,ops);
/*
Rules:
1) out-most parentheses must be open in direction to center
e.g.: (1+2+3), 1+(2+3), 1+(2+3)+4
but not: 1)+(2+3)+(4
so: first parenthesis on the left side must be open and
the last parenthesis on the right side must be close
2) parentheses in direct neighborhood to a number must be
open in direction to the number (multiplication is
not mutual)
e.g.: 1+(2+3)+4, but not: 1+2(+3+4)
3) parentheses in direct neighborhood to an operator must be
closed in direction to the operator (multiplication is
not mutual)
e.g.: 1+(2+3)+4, but not: 1+2(+3+)4
*/
// build combinations separately not in-line
// it's already a mess, no need to add more
makeParens(0,nums.length,0,0,[],parens);
// You may take a look at the raw material here
// console.log(parens.join("\n"));
for(var i= 0;i<parens.length;i++){
var term = [];
// work on copies to reduce pointer juggling
var _ops = ops.slice(0);
var _nums = nums.slice(0);
for(var j=0;j<parens[i].length;j++){
if(parens[i][j] === '('){
term.push("(");
// rule 3
if(parens[i][j+1] === ')'){
term.push(_nums.shift());
}
// rules 1,2
else {
term.push(_nums.shift());
term.push(_ops.shift());
}
}
if(parens[i][j] === ')'){
term.push(")");
// rules 2,3
if(parens[i][j+1] !== ')')
term.push(_ops.shift());
}
}
// some pretty printing
term = term.join("");
// eval() because I didn't want to write a parser
// but if you need one...
all.push(term + " = " + eval(term));
}
return all;
}
I'm not sure if I would get hired with that abomination. Ah, to be honest: I doubt it.
But I hope it is at least a little bit helpful.

Yikes. That was tricky. Good challenge. I'm sure this could be cut way down, but it works. I used lodash and broke the various functions down to make it more flexible. Here's a jsfiddle:
https://jsfiddle.net/mckinleymedia/3e8g22Lk/8/
Oops - had to add parseInt to the addition so it doesn't add as strings.
/*
//input:
diffWaysToCompute("2 * 3 - 4 * 5");
//output:
(2*(3-(4*5))) = -34 - 2,1,0
((2*3)-(4*5)) = -14 - 0,2,1 & 2,0,1
((2*(3-4))*5) = -10 - 1,0,2
(2*((3-4)*5)) = -10 - 1,2,0
(((2*3)-4)*5) = 10 - 0,1,2
*/
'use strict'
var diffWaysToCompute = function(str) {
var opsAvailable = ['+','-','/','*'],
numbers = [],
operators = [],
getNumbersAndOperators = function(str) {
var arr = str.split(" ");
for (var i in arr) {
if ( opsAvailable.indexOf( arr[i] ) > -1 ) {
operators.push( arr[i] );
} else {
numbers.push( arr[i] );
}
};
return;
},
permutator = function(range) {
var results = [];
function permute(arr, memo) {
var cur,
memo = memo || [];
for (var i in arr) {
cur = arr.splice(i, 1);
if (arr.length === 0) results.push(memo.concat(cur));
permute(arr.slice(), memo.concat(cur));
arr.splice(i, 0, cur[0]);
}
return results;
}
return permute(_.range(range));
},
equations = function( perms ) {
var results = [];
_.each(perms, function( perm, k ) {
results[k] = nest ( perm );
});
return results;
},
nest = function( perm ) {
var eqs = eqs || [],
ref = ref || _.range(perm.length).map(function () { return undefined }),
eq,
target = undefined;
for (var i in perm) {
var cur = perm[i],
next = perm[i] + 1,
n1 = numbers[ cur ],
n2 = numbers[ next ],
r1 = ref[ cur ],
r2 = ref[ next ];
if ( r1 !== undefined) n1 = eqs [ r1 ];
if ( r2 !== undefined) n2 = eqs [ r2 ];
var rNew;
rNew = eqs.length;
for (var x in ref ) {
if ( ( ref[ x ] !== undefined ) && ( ref[ x ] == r1 || ref[ x ] == r2 ) ) ref[ x ] = eqs.length;
};
ref[ cur ] = ref[ next ] = eqs.length;
eqs.push({
ops: operators[ cur ],
nums: [ n1, n2 ]
});
};
return eqs[ eqs.length - 1 ];
},
calculations = function ( eqs ) {
var results = []
_.each(eqs, function(equation) {
results.push(calculate( equation ));
});
return results;
},
calculate = function( eq ) {
var result = {
text: ""
};
// result.eq = eq;
result.text += "( ";
result.total = eq.nums[ 0 ];
if ( _.isObject(result.total) ) {
var result1 = calculate( result.total );
result.total = result1.total;
result.text += result1.text;
} else {
result.text += eq.nums[ 0 ];
}
_.each(eq.ops, function (op, k) {
var num = eq.nums[ k + 1 ];
result.text += " " + op + " ";
if ( _.isObject(num) ) {
var result2 = calculate( num );
num = result2.total;
result.text += result2.text;
} else {
result.text += num;
}
if ( op === '+') result.total = parseInt(result.total) + parseInt(num);
if ( op === '-') result.total = result.total - num;
if ( op === '/') result.total = result.total / num;
if ( op === '*') result.total = result.total * num;
});
result.text += " )";
return result;
},
display = function( as ) {
var target = document.getElementById('result');
target.innerHTML += '<h3 class="problem">String given: ' + str + '</h3>';
target.innerHTML += '<h4>Permutations</h4>';
_.each( as, function(a) {
target.innerHTML += '<div class="permutation">';
target.innerHTML += ' <span class="formula">' + a.text + '</span> = ';
target.innerHTML += ' <span class="total">' + a.total + '</span>';
target.innerHTML += '</div>';
});
},
perms,
eqs,
answers;
getNumbersAndOperators(str);
perms = permutator( operators.length );
eqs = equations( perms );
answers = calculations( eqs );
answers = _.uniq(answers, 'text');
display(answers);
return answers;
};
console.log(diffWaysToCompute("2 * 3 - 4 * 5"));

How do you return the resulting object in a function?

Good day, all! :)
For the past month, I have been working on a function to return 2 or more THREE.js materials in 1 function at 1 time. I've run into a small problem though. For some reason, I can't get this function to return the MeshBasicMaterial object AS WELL AS the MeshLambertMaterial data object. I KNOW my code is right because I've gone over it over 40 times already looking for errors.
Here's the WHOLE code:
/**
* A function for converting hex <-> dec w/o loss of precision.
*
* The problem is that parseInt("0x12345...") isn't precise enough to convert
* 64-bit integers correctly.
*
* Internally, this uses arrays to encode decimal digits starting with the least
* significant:
* 8 = [8]
* 16 = [6, 1]
* 1024 = [4, 2, 0, 1]
*/
// Adds two arrays for the given base (10 or 16), returning the result.
// This turns out to be the only "primitive" operation we need.
function add(x, y, base)
{
var z = [];
var n = Math.max(x.length, y.length);
var carry = 0;
var i = 0;
while (i < n || carry)
{
var xi = i < x.length ? x[i] : 0;
var yi = i < y.length ? y[i] : 0;
var zi = carry + xi + yi;
z.push(zi % base);
carry = Math.floor(zi / base);
i++;
}
return z;
}
// Returns a*x, where x is an array of decimal digits and a is an ordinary
// JavaScript number. base is the number base of the array x.
function multiplyByNumber(num, x, base)
{
if (num < 0) return null;
if (num == 0) return [];
var result = [];
var power = x;
while (true)
{
if (num & 1)
{
result = add(result, power, base);
}
num = num >> 1;
if (num === 0) break;
power = add(power, power, base);
}
return result;
}
function parseToDigitsArray(str, base)
{
var digits = str.split('');
var ary = [];
for (var i = digits.length - 1; i >= 0; i--)
{
var n = parseInt(digits[i], base);
if (isNaN(n)) return null;
ary.push(n);
}
return ary;
}
function convertBase(str, fromBase, toBase)
{
var digits = parseToDigitsArray(str, fromBase);
if (digits === null) return null;
var outArray = [];
var power = [1];
for (var i = 0; i < digits.length; i++)
{
// invariant: at this point, fromBase^i = power
if (digits[i])
{
outArray = add(outArray, multiplyByNumber(digits[i], power, toBase), toBase);
}
power = multiplyByNumber(fromBase, power, toBase);
}
var out = '';
for (var i = outArray.length - 1; i >= 0; i--)
{
out += outArray[i].toString(toBase);
}
return out;
}
function decToHex(decStr) {
var hex = convertBase(decStr, 10, 16);
return hex ? '0x' + hex : null;
}
function hexToDec(hexStr) {
if (hexStr.substring(0, 2) === '0x') hexStr = hexStr.substring(2);
hexStr = hexStr.toLowerCase();
return convertBase(hexStr, 16, 10);
}
function instr(str, val)
{
if(typeof(str) === 'string')
{
str = str.toString(str);
val = val.toString(val);
in_str = str.indexOf(val);
return in_str;
}
else
{
api_messagebox('Please use a string!');
}
return false;
}
function Get_RGBA(hexVal, getwhich)
{
hexVal = hexVal || '';
getwhich = getwhich || 0;
var commaSeperated = 0;
//if(typeof(hexVal) === 'string')
//{
// Removes the first character from the input string
if(hexVal.length === 8) { hexVal = hexVal.substring(1, hexVal.length); }
if(hexVal.length === 10) { hexVal = hexVal.substring(0, hexVal.length); }
// Now let's separate the pairs by a comma
for (var i = 0; i <= hexVal.length; i++)
{
// Iterate through each char of hexVal
// Copy each char of hexVal to commaSeperated
commaSeperated += hexVal.charAt(i);
// After each pair of characters add a comma, unless this
// is the last char
commaSeperated += (i % 2 == 1 && i != (hexVal.length - 1)) ? ',' : '';
}
// Lets now remove the 0x
if(instr(commaSeperated, '0x'))
{
commaSeperated = commaSeperated.substr(4);
}
if(instr(commaSeperated, ','))
{
// Lets now remove all "," 's
commaSeperated = commaSeperated.replace(/,/g, '');
if( getwhich < 0 ) { getwhich = 0; }
if( getwhich > 5 ) { getwhich = 5; }
alpha = [];
red = [];
green = [];
blue = [];
allcol = [];
sixcol = [];
alpha[0] = commaSeperated[0]+commaSeperated[1];
red[0] = commaSeperated[2]+commaSeperated[3];
green[0] = commaSeperated[4]+commaSeperated[5];
blue[0] = commaSeperated[6]+commaSeperated[7];
allcol[0] = alpha[0]+red[0]+green[0]+blue[0];
sixcol[0] = red[0]+green[0]+blue[0];
if( getwhich === 0 ) { fi_string = alpha[0]; }
if( getwhich === 1 ) { fi_string = red[0]; }
if( getwhich === 2 ) { fi_string = green[0]; }
if( getwhich === 3 ) { fi_string = blue[0]; }
if( getwhich === 4 ) { fi_string = allcol[0]; }
if( getwhich === 5 ) { fi_string = sixcol[0]; }
if( getwhich === 4 && fi_string.length != 10 || fi_string.length != 9 ) { getwhich = 5; }
if( getwhich === 5 && fi_string.length != 8 || fi_string.length != 7 ) { getwhich = 4; }
// Split the commaSeperated string by commas and return the array
return fi_string.toString();
}
//}
}
function isArray(myArray)
{
return myArray.constructor.toString();
//myArray.constructor.toString().indexOf("Array") > -1;
}
//EntityMaterial(0, 0, 0xFF44CFFC, 1, 0xFF000000, 4, 4, 0, 1.0, 0.8, "LambertBasicMaterial", 1)
function EntityMaterial(ptex, side, color, wire, wirecolor, col_type, col_wire_type, shading, transparent, opacity, mat_type, overdraw)
{
ptex = ptex || 0;
side = side || 0;
color = color || 0xFF006400;
wire = wire || 0;
wirecolor = wirecolor || 0xFF006400;
col_type = col_type || 4;
col_wire_type = col_wire_type || 4;
shading = shading || false;
transparent = transparent || 0.0;
opacity = opacity || 1.0;
mat_type = mat_type || "BasicMaterial";
overdraw = overdraw || true;
color = decToHex(color.toString());
wirecolor = decToHex(wirecolor.toString());
var gRGBA1 = Get_RGBA(color, col_type);
var gRGBA2 = Get_RGBA(wirecolor, col_wire_type);
var mat = 0;
if(mat_type === 'BasicMaterial')
{
this.materials = new THREE.MeshBasicMaterial
(
{
color: parseInt(gRGBA1, 16)
}
)
}
else if(mat_type === 'LambertMaterial')
{
this.materials = new THREE.MeshLambertMaterial
(
{
color: parseInt(gRGBA2, 16),
opacity: opacity,
wireframe: wire,
transparent: transparent
}
)
}
else if(mat_type === 'LambertBasicMaterial')
{
//new empty array.. could also be written as this.materials = new Array();
this.materials = [];
var mats = this.materials;
var basicMat = new THREE.MeshBasicMaterial( { color: parseInt(gRGBA1, 16) } );
var lambertMat = new THREE.MeshLambertMaterial( { color: parseInt(gRGBA2, 16), opacity: opacity, wireframe: wire, transparent: transparent } );
mats.push(basicMat);
mats.push(lambertMat);
api_messagebox(mats);
return mats;
}
}
Thank you so much!
Sincerely,
~Mythros

Right, I finally got around to trying it out and it all runs well for me.
To make sure we don't have any differences in environments take a look at the fiddle I made and let me know if it works for you as expected or if there's any other problems you need help with:
JSFiddle of original code
Small changes:
commented out the
api_messagebox(mats)
as it's undefined.
added lots of log statements so check out the web console.
Edit
I fixed the color problem by using THree.js' Color object as follows:
var color = new THREE.Color("rgb(0,0,255)");
But you may be doing this somewhere as the GET_RGBA function you are calling seems to be missing from the code you gave me.
As to making it wiremesh, I checked the Lambert object and it definitely had wiremesh = 1 set.
Make sure that the wire var you're passing is actually set to true, I set it explicitly in this updated fiddle