Develop Reference

Why aren't the bigInts adding?

I made a NodeJS program that takes pairs of integers (m, n) as input and prints the sum of their factorials (facm, factn) on the console. I used the BigInteger.js library so that I can calculate using big numbers.
But when I input 20 1, the program just outputs the value of 20! instead of 20! + 1!. It doesn't add. Why?
(For some reason, it works for when the two inputs are the same, for example, 20 20. It also works when the values are smaller.)
var input = require('fs').readFileSync('/dev/stdin', 'utf8');
var lines = input.split('\n');
var bigInt = require("big-integer");
for (var i = 0; lines[i] != ""; i++) {
var strings = lines[i].split(" ");
var m = parseInt(strings[0]);
var n = parseInt(strings[1]);
var factm = bigInt(1);
var factn = bigInt(1);
for (var a = m; a != 0; a--) {
factm = factm.multiply(a);
}
for (var b = n; b != 0; b--) {
factn = factn.multiply(b);
}
var sum = factm.add(factn);
console.log(sum.toString());
}

Replacing var sum = factm.add(factn) with var sum = factm.add(factn.toString()) solves the problem.

"Look and say sequence" in javascript

1
11
12
1121
122111
112213
122211
....
I was trying to solve this problem. It goes like this.
I need to check the former line and write: the number and how many time it was repeated.
ex. 1 -> 1(number)1(time)
var antsArr = [[1]];
var n = 10;
for (var row = 1; row < n; row++) {
var lastCheckedNumber = 0;
var count = 1;
antsArr[row] = [];
for (var col = 0; col < antsArr[row-1].length; col++) {
if (lastCheckedNumber == 0) {
lastCheckedNumber = 1;
antsArr[row].push(lastCheckedNumber);
} else {
if (antsArr[row-1][col] == lastCheckedNumber) {
count++;
} else {
lastCheckedNumber = antsArr[row-1][col];
}
}
}
antsArr[row].push(count);
antsArr[row].push(lastCheckedNumber);
}
for (var i = 0; i < antsArr.length; i++) {
console.log(antsArr[i]);
}
I have been on this since 2 days ago.
It it so hard to solve by myself. I know it is really basic code to you guys.
But still if someone who has a really warm heart help me out, I will be so happy! :>

Try this:
JSFiddle Sample
function lookAndSay(seq){
var prev = seq[0];
var freq = 0;
var output = [];
seq.forEach(function(s){
if (s==prev){
freq++;
}
else{
output.push(prev);
output.push(freq);
prev = s;
freq = 1;
}
});
output.push(prev);
output.push(freq);
console.log(output);
return output;
}
// Sample: try on the first 11 sequences
var seq = [1];
for (var n=0; n<11; n++){
seq = lookAndSay(seq);
}
Quick explanation
The input sequence is a simple array containing all numbers in the sequence. The function iterates through the element in the sequence, count the frequency of the current occurring number. When it encounters a new number, it pushes the previously occurring number along with the frequency to the output.
Keep the iteration goes until it reaches the end, make sure the last occurring number and the frequency are added to the output and that's it.

I am not sure if this is right,as i didnt know about this sequence before.Please check and let me know if it works.
var hh=0;
function ls(j,j1)
{
var l1=j.length;
var fer=j.split('');
var str='';
var counter=1;
for(var t=0;t<fer.length;t++)
{
if(fer[t]==fer[t+1])
{
counter++;
}
else
{
str=str+""+""+fer[t]+counter;
counter=1;
}
}
console.log(str);
while(hh<5) //REPLACE THE NUMBER HERE TO CHANGE NUMBER OF COUNTS!
{
hh++;
//console.log(hh);
ls(str);
}
}
ls("1");

You can check out the working solution for in this fiddle here
You can solve this by splitting your logic into different modules.
So primarily you have 2 tasks -
For a give sequence of numbers(say [1,1,2]), you need to find the frequency distribution - something like - [1,2,2,1] which is the main logic.
Keep generating new distribution lists until a given number(say n).
So split them into 2 different functions and test them independently.
For task 1, code would look something like this -
/*
This takes an input [1,1,2] and return is freq - [1,2,2,1]
*/
function find_num_freq(arr){
var freq_list = [];
var val = arr[0];
var freq = 1;
for(i=1; i<arr.length; i++){
var curr_val = arr[i];
if(curr_val === val){
freq += 1;
}else{
//Add the values to the freq_list
freq_list.push([val, freq]);
val = curr_val;
freq = 1;
}
}
freq_list.push([val, freq]);
return freq_list;
}
For task 2, it keeps calling the above function for each line of results.
It's code would look something like this -
function look_n_say(n){
//Starting number
var seed = 1;
var antsArr = [[seed]];
for(var i = 0; i < n; i++){
var content = antsArr[i];
var freq_list = find_num_freq(content);
//freq_list give an array of [[ele, freq],[ele,freq]...]
//Flatten so that it's of the form - [ele,freq,ele,freq]
var freq_list_flat = flatten_list(freq_list);
antsArr.push(freq_list_flat);
}
return antsArr;
}
/**
This is used for flattening a list.
Eg - [[1],[1,1],[1,2]] => [1,1,1,1,2]
basically removes only first level nesting
**/
function flatten_list(li){
var flat_li = [];
li.forEach(
function(val){
for(ind in val){
flat_li.push(val[ind]);
}
}
);
return flat_li;
}
The output of this for the first 10 n values -
OUTPUT
n = 1:
[[1],[1,1]]
n = 2:
[[1],[1,1],[1,2]]
n = 3:
[[1],[1,1],[1,2],[1,1,2,1]]
n = 4:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1]]
n = 5:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1],[1,1,2,2,1,3]]
n = 6:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1],[1,1,2,2,1,3],[1,2,2,2,1,1,3,1]]
n = 7:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1],[1,1,2,2,1,3],[1,2,2,2,1,1,3,1],[1,1,2,3,1,2,3,1,1,1]]
n = 8:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1],[1,1,2,2,1,3],[1,2,2,2,1,1,3,1],[1,1,2,3,1,2,3,1,1,1],[1,2,2,1,3,1,1,1,2,1,3,1,1,3]]
n = 9:
[[1],[1,1],[1,2],[1,1,2,1],[1,2,2,1,1,1],[1,1,2,2,1,3],[1,2,2,2,1,1,3,1],[1,1,2,3,1,2,3,1,1,1],[1,2,2,1,3,1,1,1,2,1,3,1,1,3],[1,1,2,2,1,1,3,1,1,3,2,1,1,1,3,1,1,2,3,1]]

how to calculate values of an (javascript) object with date keys

I have the following simplified (javascript) object, of which properties are dates (in string fomat):
Given a random startdate and enddate within the range of dates in the object, how to code (efficiently) the calculation - say accumulate- of the values within this range? As an example, for the following code the calculation result should be 12 (3+4+5) for the given startdate and enddate.
var startdate = '2014-01-03';
var enddate = '2014-01-05'
var obj = {};
obj['2014-01-02'] = '2';
obj['2014-01-03'] = '3';
obj['2014-01-04'] = '4';
obj['2014-01-05'] = '5';
obj['2014-01-06'] = '6';

You can just loop through the properties of the object, doing a comparison, and adding.
var startdate = '2014-01-04';
var enddate = '2014-01-05';
var arr = {};
arr['2014-01-02'] = '2';
arr['2014-01-03'] = '3';
arr['2014-01-04'] = '4';
arr['2014-01-05'] = '5';
arr['2014-01-06'] = '6';
var total = 0;
for(var p in arr) {
if(arr.hasOwnProperty(p)) {
if(new Date(p) >= new Date(startdate) && new Date(p) <= new Date(enddate)) {
total += parseInt(arr[p], 10);
}
}
}
console.log(total);
Sample http://jsbin.com/imUdewaJ/1/edit
I'm sure there is a better way to do this, but I don't know how due to having to parse the date object out for comparison.
--Edit added in the hasOwnProperty check from comments below

When doing stuff with dates, you might want to use thirdparty tools to handle browser compatibility. Momentjs is a good one for dates.
solution with momentjs:
var startdate = moment('2014-01-03');
var enddate = moment('2014-01-05');
var obj = {};
obj['2014-01-02'] = '2';
obj['2014-01-03'] = '3';
obj['2014-01-04'] = '4';
obj['2014-01-05'] = '5';
obj['2014-01-06'] = '6';
var strDate;
var total = 0;
for (strDate in obj) {
if (obj.hasOwnProperty(strDate)) {
var date = moment(strDate)
if (date.diff(startdate, 'days')>=0 && date.diff(enddate, 'days')<=0) {
total += parseInt(obj[strDate], 10);
}
}
}
console.log(total);

It's possible that some browsers won't support date1 > date2, so it might be better to also use getTime().
function getDate(date) {
return new Date(date).getTime();
}
function getTotal(start, end) {
var total = 0;
for (var k in obj) {
var current = getDate(k);
if (current >= start && current <= end) {
total += parseInt(obj[k], 10);
}
}
return total;
}
var start = getDate(startdate);
var end = getDate(enddate);
console.log(getTotal(start, end)); // 12

I want to add all the values in the field Sum to the field Total but it is not working

Here, sums[i].value is getting right values but when I want to keep a grand total of all Sum, it is failing.
function calc() {
var amounts = document.getElementsByName("Amount");
var prices = document.getElementsByName("Price");
var sums = document.getElementsByName('Sum');
var tax = document.getElementsByName('Tax');
var total = document.getElementsByName('Total');
for (var i = 0; i < amounts.length; i++) {
sums[i].value = amounts[i].value * prices[i].value;
total[0].value = total[0].value + sums[i].value;
// only this line is not working
}
}

Plain HTML is strings, all the way down, and var amounts = document.getElementsByName("Amount"); followed by amounts.value means you now have string values. Since + is also a string operator, JavaScript will happily turn "2"+"4" into "24", which looks like it did maths, but wrong, when in fact it didn't do math at all.
Convert all values that need to be numbers into numbers, first:
var amounts = document.getElementsByName("Amount");
....
var amount = parseFloat(amounts.value); // NOW it's a number
...

Replace your code with :
for (var i = 0; i < amounts.length; i++) {
sums[i].value = parseFloat(amounts[i].value) * parseFloat(prices[i].value);
total[0].value = parseFloat(total[0].value) + parseFloat(sums[i].value);
// only this line is not working
}

sums[i].value = parseFloat(amounts[i].value) * parseFloat(prices[i].value);
total[0].value = parseFloat(total[0].value) + parseFloat(sums[i].value);
This should help you.

Remove the .value while adding and multiplying
function test()
{
var amounts = new Array();
amounts[0] = "4";
amounts[1] = "6";
amounts[2] = "10";
var prices = new Array();
prices[0] = "4";
prices[1] = "6";
prices[2] = "10";
var sums = new Array();
var total = 0;
for (var i = 0; i < amounts.length; i++) {
sums[i] = parseInt(amounts[i]) * parseInt(prices[i]);
total= parseInt(total) + parseInt(sums[i]);
// only this line is not working
//alert(total); is 152
}
}

How do I convert a string into a bitmask in javascript?

Now, this is simple enough when the numbers are small, but numbers like "9223372036854775807" are too large for parseInt().
I'm not sure how to do this within the Google docs script editor, which doesn't seem to allow for external classes.

Here you go, used this script somewhere and it seems to work. The idea behind it is that it splits the string to 8-character chunks, and calculates chunk/2, then sums the chunks up and gets a result of division by 2.
By dividing by 2 - it easily calculates the result then.
var maxIntSize = 8;
function divide2(number, addup, depth) {
var result = "";
var partLength = Math.min(number.length,maxIntSize);
var part = number.substring(0,partLength);
var partNum = parseInt(part,10);
var partAdd = (addup==0)?0:(5*Math.pow(10,partLength-1));
var partRes = Math.floor(partNum/2)+partAdd;
var partRem = partNum%2;
result = result + partRes;
if (depth > 0) {
for (var i=result.length; i < partLength; i++) {
result = "0"+result;
}
}
var nextPart = number.substring(partLength, number.length);
if (partLength < number.length) {
var res = divide2(nextPart, partRem, depth+1);
result = result + res.result;
res.result = result;
return res;
} else {
var res = {result: result, remainder: partRem};
return res;
}
}
function toBinary(number) {
var out = "";
while (number.length > 1 || number != "0") {
var res = divide2(number,0,0);
out = "" + res.remainder + out;
number = res.result;
}
return out;
}
var testNum = "12312312312112312312312312312312312312312312312312312312312312312312312312312312312312312312123";
document.write("bin("+testNum+") = "+toBinary(""+testNum)+"<br/>");
Division to chunks is required to calculate division by 2 faster. This script works pretty fast even for huge numbers.