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?

Related problem: Reverse Integer

難度係數：

容易

實現

uint32_t reverseBits(uint32_t n) {
    static uint32_t key = 0;
    static uint32_t val = 0;
    if (n == key) return val;
    if (n == val) return key;
    uint32_t ret = 0;
    int index = 31;
    key = n;
    while (n > 0) {
        ret |= (n & 0x1) << index;
        n >>= 1;
        index--;
    }
    val = ret;
    return val;
}