0201. Bitwise AND of Numbers Range

https://leetcode.com/problems/bitwise-and-of-numbers-range

Description

Given two integers left and right that represent the range [left, right], return the bitwise AND of all numbers in this range, inclusive.

Example 1:

**Input:** left = 5, right = 7
**Output:** 4

Example 2:

**Input:** left = 0, right = 0
**Output:** 0

Example 3:

**Input:** left = 1, right = 2147483647
**Output:** 0

Constraints:

• 0 <= left <= right <= 231 - 1

ac

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

/**
1. if there is 0 in that digit, then it's 0 all the time.
2. odd & even, last digit is 0
3. if m != n, there must be one odd and one even, at least. so last digit is 0
4. shift m and n right 1 digit every time util they are equal
5. when m == n, move back, all digits on the right should be 0
**/