Leetcode: Bitwise AND of Numbers Range

Given a range [m, n] where 0 <= m <= n <= 2147483647, return the bitwise AND of all numbers in this range, inclusive.

For example, given the range [5, 7], you should return 4.

Credits:
Special thanks to @amrsaqr for adding this problem and creating all test cases.

Understand the problem:
We could take several examples, e.g. 5 6 7
101
110
111
-------
100

We could find out that the trick of the problem is when compare bit-by-bit for each number, once they are the same, e.g. bit 1 for the most significant bit, they start to be the same. 

9 10 11 12
1001
1010
1011
1100
---------
1000

So the solution is shift both m and n to the right until they are the equal, count the number of steps it shifted. Then shift m left to the number of steps. 

Code (Java):

public class Solution {
    public int rangeBitwiseAnd(int m, int n) {
        int shift = 0;
        
        while (m != n) {
            shift++;
            m = m >> 1;
            n = n >> 1;
        }
        
        return m << shift;
    }
}