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Description：

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 should return 3.

Code：

int hammingWeight(uint32_t n) {
        int num = 0;
        while (n)
        {
            n = n & (n-1);
            ++num;
        }
        return num;
    }