1.描述

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?

2.分析

3.代码

uint32_t reverseBits(uint32_t n) {
    uint32_t result = n;
    result = ((result & 0xffff0000) >>16) | ((result & 0x0000ffff) << 16);
    result = ((result & 0xff00ff00) >> 8) | ((result & 0x00ff00ff) << 8);
    result = ((result & 0xf0f0f0f0) >> 4) | ((result & 0x0f0f0f0f) << 4);
    result = ((result & 0xcccccccc) >> 2) | ((result & 0x33333333) << 2);
    result = ((result & 0xaaaaaaaa) >> 1) | ((result & 0x55555555) << 1);
    return result;
}