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.

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


=======

public class Solution {
    public int rangeBitwiseAnd(int m, int n) {
        int mask = ~0;
        while ((m & mask) != (n & mask)) {
            mask <<= 1;
        }
        return mask & n;
    }
}