201. Bitwise AND of Numbers Range

发布时间：2020-12-14 05:18:33 所属栏目：大数据来源：网络整理

导读：https://leetcode.com/problems/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.Example 1 :Input: [ 5,7 ]Output: 4 Example 2 :Input: [ 0,1 ]Output:

https://leetcode.com/problems/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.

Example 1:

Input: [5,7]
Output: 4
Example 2:

Input: [0,1]
Output: 0

解题思路：

先硬来，超时。

看大神的解法，结论是这道题其实就是要找m和n的bit common prefix。而不需要从m一直算到n。

The hardest part of this problem is to find the regular pattern.
For example,for number?26 to 30
Their binary form are:
11010
11011
11100　　
11101　　
11110

https://leetcode.com/problems/bitwise-and-of-numbers-range/discuss/56729/Bit-operation-solution(JAVA)

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

（编辑：李大同）

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