CODEWITHSUNDEEP
javascript
Roscoe
Roscoe

Reputation: 179

Count Bits from unsigned integer

I am attempting to write a function that takes an (unsigned) integer as input, and returns the number of bits that are equal to one in the binary representation of that number.

Example: The binary representation of 1234 is 10011010010, so the function should return 5 in this case.

Here is my answer:

var newArr;
var count = 0;
function countBits(num){
    newArr = num.toString(2).split('').map(function(el){
        if(el == '1')
            count++
    });;
    return count;  
}

In my program when I call countBits(7) it returns //3 but when I submit my response it says it is returning //4. Can someone see what I am missing in my response based on question?

Upvotes: 0

Views: 3729

Answers (3)

white shadow
white shadow

Reputation: 11

function countBits(num){

    // convert num Base10 to Base2
    let base2 = num.toString(2)

    // declare variable for sum of bits 
    let sum = 0

    // for loop to check bits (bit = 1) and ignore Zeros in the String base2 
    for(let i = 0; i <  base2.length; i++){
        if(base2[i] == 1){
            // use Number() to convert string to number
            count += Number(base2[i])
        } 
    }
    return sum ;

}

Upvotes: 0

white shadow
white shadow

Reputation: 11

function countBits(num){

    /* Convert num Base10 to num Base2 
    then find Ones and save them in an array
    length of the array is equal their sum */

    return num.toString(2).match(/1/g).length
}

Upvotes: 0

Bergi
Bergi

Reputation: 664548

Your problem is that you are declaring the variables outside of the function, so when the function is called multiple times they'll keep their values and just increase the count.

Btw, you also shouldn't use map if you don't want to create another array - so better do

function countBits(num){
    var newArr = num.toString(2).split('').map(Number);
    var count = 0;
    for (var i=0; i<newArr.length; i++)
        count += newArr[i];
    }
    return count;  
}

or

function countBits(num){
    return num.toString(2).split('').reduce(function(count, el) {
        return count + (el == "1");
    }, 0);
}

Upvotes: 3

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