Question

How to count the number of bits to be flipped to convert a number to another number in JavaScript

Answer 1

function countBits(num1, num2) {
    let count = 0;
    let lsb1 = 0;
    let lsb2 = 0;
        
    while ((num1 > 0) || (num2 > 0)) {
        lsb1 = num1 & 1;
        lsb2 = num2 & 1;
        
        if (lsb1 != lsb2) {
            count++;
        }
        
        num1 = num1 >> 1;
        num2 = num2 >> 1;
    }
    
    return count;
}

let num1 = 2;  // 00000010
let num2 = 17; // 00010001

console.log("Number of bits to be flipped : " + countBits(num1, num2));

num1 = 3;   // 00000011
num2 = 221; // 11011101

console.log("Number of bits to be flipped : " + countBits(num1, num2));

 
 
 
 
/*
run:
   
Number of bits to be flipped : 3
Number of bits to be flipped : 6
       
*/

 

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Answer 2

function countBits(num1, num2) {
    let n = num1 ^ num2;
    let count = 0;
       
    while (n > 0) {
        count++;
        n &= (n - 1);
    }
     
    return count;
}
 
let num1 = 2;  // 00000010
let num2 = 17; // 00010001
 
console.log("Number of bits to be flipped : " + countBits(num1, num2));
 
num1 = 3;   // 00000011
num2 = 221; // 11011101
 
console.log("Number of bits to be flipped : " + countBits(num1, num2));
 
  
  
  
  
  
/*
run:
    
Number of bits to be flipped : 3
Number of bits to be flipped : 6
        
*/

 

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