[Algorithm] 6 week(2.14 ~ 20) 3/3

1356. Sort Integers by The Number of 1 Bits

var sortByBits = function(arr) {
   const sortedArr = arr.sort((a, b) => (numBits(a) - numBits(b)) || ( a - b));
    
    return sortedArr;
};

const memo = { 0 : 0 };

   
function numBits(num) {
    if(memo[num] !== undefined) return memo[num];
 
    return memo[num] = (num & 1) + numBits(num >> 1);
}