【LeetCode】190 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 as 00111001011110000010100101000000).

Follow up:

If this function is called many times, how would you optimize it?

Note: Although the algorithm 2 solves the problem with one line code (using the original method in Integer.class),the algorithm 1 is faster than 2.

Algorithm 1：（Runtime：2ms）

public class Solution {
// you need treat n as an unsigned value
public int reverseBits(int n) {
int result = 0;
int index = 1;
for (int i = 0; i < 32; i++) {
if ((n & index) == index) {
result = result | (1 << (31 - i));
}

index = index << 1;
}
return result;
}
}

Algorithm 2：（Runtime：3ms）

public class Solution {
// you need treat n as an unsigned value
public int reverseBits(int n) {
return Integer.reverse(n);
}
}