【LeetCode】190. Reverse Bits

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?

Related problem: Reverse Integer

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

 

从高位开始check每一位n是0还是1，然后在低位对应位置设置相应0或者1.

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        unsigned ret = 0;
        unsigned pos1 = 1 << 31;
        unsigned pos2 = 1;
        while(pos1)
        {
            if(pos1 & n)
                ret |= pos2;
            pos2 <<= 1;
            pos1 >>= 1;
        }
        return ret;
    }
};