[leetcode-190]Reverse Bits(C)

问题描述：

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?

分析：这道题主要考察对bit位的操作。这里使用两个指针，从两端向中间逼近，每次交换对应项位置。

代码如下：4ms

[code]uint32_t reverseBits(uint32_t n) {
    uint32_t slow = 1 << 0, fast = 1 << 31;

    while (fast>slow) {
        //swap
        uint32_t slowVal = slow & n;
        uint32_t fastVal = fast & n;

        if (slowVal) {
            n |= fast;
        }
        else {
            n &= ~fast;
        }

        if (fastVal) {
            n |= slow;
        }
        else {
            n &= ~slow;
        }

        fast = fast >> 1;
        slow = slow << 1;
    }
    return n;
}