[LeetCode] Number of 1 Bits

[LeetCode] Number of 1 Bits

Write a function that takes an unsigned integer and returns the number of '1' bits it has (also known as the Hamming weight ).

For example, the 32-bit integer '11' has binary representation 00000000000000000000000000001011, so the function shocould return 3.

Solution 1

Each bitwise AND 1 are performed and calculated separately. The statistical result is not a zero-digit number.

Implementation Code 1

//Runtime:10 ms#include 
  
   #include "inttypes.h"using namespace std;class Solution {public:    int hammingWeight(uint32_t n) {        int i = 0;        while (n)        {            i += n & 0x1;            n >>= 1;        }        return i;    }};int main(){    Solution s;    cout<
   
  

Solution 2

Each n & (n-1) operation can reduce the number of digits with the value of 1 in n by one.

Implementation Code 2

//Runtime:11 msclass Solution {public:    int hammingWeight(uint32_t n) {        int i = 0;        while (n)        {            n &= (n-1);            ++i;        }        return i;    }};