LeetCode-190.Reverse Bits

https://leetcode.com/problems/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 as00111001011110000010100101000000).

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

uint32_t reverseBits(uint32_t n) 
    {
        uint32_t res=0;
    	int i = 0;
    	while (i++<32)
    	{
    		res = (res << 1) + (n & 1);
    		n >>= 1;
    	}
    	return res;
    }

技巧 参考https://leetcode.com/discuss/27405/o-1-bit-operation-c-solution-8ms

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