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?
C Solution 1:
uint32_t reverseBits(uint32_t n) {
uint32_t res = 0;
int i;
for (i = 0; i < 32; i++) {
res <<= 1;
res |= n & 1;
n >>= 1;
}
return res;
}
C Solution 2:
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;
}
Summary:
- Solution 2 is so beautiful.
LeetCode: 190. Reverse Bits
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