Friday, August 28, 2015

Leetcode: 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 as00111001011110000010100101000000).
Follow up:
If this function is called many times, how would you optimize it?
Related problem: Reverse Integer
Understand the problem:
We could get the least significant bit each time and append to the new result. 
e.g. 11100, we get 0 0 1 1 1, and append to the new result from right to left as well.

Code (Java):
public class Solution {
    // you need treat n as an unsigned value
    public int reverseBits(int n) {
        
        int result = 0;
        for (int i = 0; i < 32; i++) {
            result = (result << 1) | (n & 1);
            n = (n >> 1);
        }
        
        return result;
    }
}

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