Li Kou daily question - day 30 -1523 Number of bit 1

2022.6.28 Did you brush the questions today ？

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subject ：

Write a function , Input is an unsigned integer （ In the form of a binary string ）, Returns the number of digits in its binary expression as '1' The number of （ Also known as Hamming weight ）.

analysis ：

To give you one 32 Bit integers , for example 01, You need to find out how many there are 1, Then return the number

Ideas ： We make use of n&n-1 The formula , By changing the formula, the lowest bit of each time can be achieved 1 Turn into 0. So we put all 1 Turn into 0, Count the number of changes , Namely 1 The number of .

analysis ：

class Solution {
public:
    int hammingWeight(uint32_t n) {
        int ret = 0;
        while (n) {
            n &= n - 1;
            ret++;
        }
        return ret;
    }
};