p191

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LeetCode p191 Number of 1 Bits 题解

1.题目：

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.

题意：

输入一个整数，返回它的二进制里面有多少个1.

2.解题思路:

见代码
注意 2147483648 没有符号位会变为 - 2147483648。

3.代码

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public class Solution {
    // you need to treat n as an unsigned value
    public int hammingWeight(int n) {
        int ans = 0;
		while (n != 0) { // 2147483648 不能使用 n>0
			if ((n & 1) == 1)
				ans++;
			n = n >>> 1;
		}
		return ans;
    }
}

4.一些总结：