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# Reverse Bits

发表于 2015-03-11 分类于 leetcode 阅读次数： 阅读次数： Disqus：

### Reverse Bits

#### Reverse bits of a given 32 bits unsigned integer.

For example, given input 43261596 (represented in binary as 00000010100101000001111010011100), return 964176192 (represented in binary as 00111001011110000010100101000000).

Follow up:
If this function is called many times, how would you optimize it?

### code

    class Solution {
    public:
        uint32_t reverseBits(uint32_t n) {
            n = ((n >> 1) & 0x55555555) | ((n & 0x55555555) << 1);
            n = ((n >> 2) & 0x33333333) | ((n & 0x33333333) << 2);
            n = ((n >> 4) & 0x0f0f0f0f) | ((n & 0x0f0f0f0f) << 4);
            n = ((n >> 8) & 0x00ff00ff) | ((n & 0x00ff00ff) << 8);
            n = ((n >> 16) & 0x0000ffff) | ((n & 0x0000ffff) << 16);
            return n;
        }
    };