201. 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.

这道题的技巧是：

1. 若m != n，则最后一位必然是0；
2. 每次将m，n右移一位直到m == n，并设一个factor来记录iteration次数。

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