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Asked: 2026-06-10T03:51:52+00:00

I am trying to write a program in javascript that gets an unspecified number

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I am trying to write a program in javascript that gets an unspecified number of numbers out of a html textarea and tries all combinations (adding all numbers with eachother) to see if it mathches a number you specified.

Now I can make an array out of the string in the textarea and using for loops I add these up (see below code). The problem how can you do this for an unspecified number of numbers that are to be added up (e.g. adding up 7 different number if you enter 7 numbers in textarea)? I was thinking of using a second array and, which gets the numbers to add up out of the first loop. And then make te lenght of the loop variable by using a for loop with the lenght of the array containing all numbers (lines in my example) as endvalue.

How can I fill in the values of this 2nd array, making sure all combinations are used?

By the way, I wanted this code because I am a auditor. Sometimes a client reverses a couple of amounts in one booking, without any comment. This code will make it a lot easier to check what bookings have been reversed

edit: The awnser of cheeken seems to be working I only have one remark. What if multiple sub sets of your power set added up result in the number you are looking for? e.g.:findSum([1,2,3,4,5],6) can result [1,2,3] but also [2,4] or [1,5]. is it possible to let the function return multiple sub sets?

Found the answer my self 🙂
I replaced code

return numberSet;

By

document.getElementById("outp").value=document.getElementById("outp").value+ numberSet +"\n";

Thank you very much Cheeken

One more additional question. How do i format the input for parsing that function? The code below doesn’t seem to work. inp is the ID of the textarea where the input is (the numbers are seperated with a semicolumn. The variable ge works so there is no problem there (tested it with [1,2,3,4] and it worked. What is wrong with this code?

re edit:

found the solution. The array needed to be parsed as a floating number added this code.`

for (var i=0; i < lines.length; i++) {
    lines[i]= parseFloat(lines[i]);
    }


findSum(document.getElementById("inp").value.split(";"), ge);

Code: 

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
function powerset(arr) {
    var ps = [[]];
    for (var i=0; i < arr.length; i++) {
        for (var j = 0, len = ps.length; j < len; j++) {
            ps.push(ps[j].concat(arr[i]));
        }
    }
    return ps;
}

function sum(arr) {
    var total = 0;
    for (var i = 0; i < arr.length; i++)
        total += arr[i];
    return total
}

function findSum(numbers, targetSum) {
    var numberSets = powerset(numbers);
    for (var i=0; i < numberSets.length; i++) {
        var numberSet = numberSets[i]; 
        if (sum(numberSet) == targetSum)
            document.getElementById("outp").value=document.getElementById("outp").value+ numberSet +"\n"; 
    }
}

function main()
{

ge= document.getElementById("getal").value;
findSum([1,1,0.5,0.1,0.2,0.2], ge);


}


</script>
</head>
<body>

<input type="button" onclick="main()" value="tel" /><input type="text" id="getal" /><br>
input<br><textarea id="inp"  ></textarea><br>
output<br><textarea id="outp" ></textarea><br>
document.getElementById("inp").value.split(";")
</body>
</html>
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1 Answer

  1. Editorial Team

    More concretely, you’re looking for a particular sum of each set in the power set of your collection of numbers.

    You can accomplish this with the following bit of code.

    function powerset(arr) {
    var ps = [[]];
    for (var i=0; i < arr.length; i++) {
        for (var j = 0, len = ps.length; j < len; j++) {
            ps.push(ps[j].concat(arr[i]));
        }
    }
    return ps;
}

function sum(arr) {
    var total = 0;
    for (var i = 0; i < arr.length; i++)
        total += arr[i];
    return total
}

function findSum(numbers, targetSum) {
    var numberSets = powerset(numbers);
    for (var i=0; i < numberSets.length; i++) {
        var numberSet = numberSets[i]; 
        if (sum(numberSet) == targetSum)
            return numberSet;
    }
}

    Example invocation:

    >> findSum([1,2,3,4,5],6)
[1, 2, 3]
>> findSum([1,2,3,4,5],0)
[]
>> findSum([1,2,3,4,5],11)
[1, 2, 3, 5]

    If you’d like to collect all of the subsets whose sum is the value (rather than the first one, as implemented above) you can use the following method.

    function findSums(numbers, targetSum) {
    var sumSets = [];
    var numberSets = powerset(numbers);
    for (var i=0; i < numberSets.length; i++) {
        var numberSet = numberSets[i]; 
        if (sum(numberSet) == targetSum)
            sumSets.push(numberSet);
    }
    return sumSets;
}

    Example invocation:

    >> findSums([1,2,3,4,5],5);
[[2,3],[1,4],[5]]
>> findSums([1,2,3,4,5],0);
[[]]
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