190. Reverse Bits

32位无符号整数的位反转

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本文介绍了一种高效的方法来实现32位无符号整数的位反转。通过逐步移位和位操作，该算法能够在常数时间内完成位反转任务，适用于需要快速进行位操作的应用场景。

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).

class Solution {
public:
    uint32_t reverseBits(uint32_t n) {
        string s = "";
        for(int i = 31; i >= 0; --i){
            s += (n % 2) + '0';
            n >>= 1;
        }
        std::bitset<32> bval(s);
        return bval.to_ulong();
    }
};

class Solution {
public:
    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;
    }
};