leetcode讲解--868. Binary Gap

题目

Given a positive integer N, find and return the longest distance between two consecutive 1's in the binary representation of N.

If there aren't two consecutive 1's, return 0.

Example 1:

Input: 22
Output: 2
Explanation: 
22 in binary is 0b10110.
In the binary representation of 22, there are three ones, and two consecutive pairs of 1's.
The first consecutive pair of 1's have distance 2.
The second consecutive pair of 1's have distance 1.
The answer is the largest of these two distances, which is 2.

Example 2:

Input: 5
Output: 2
Explanation: 
5 in binary is 0b101.

Example 3:

Input: 6
Output: 1
Explanation: 
6 in binary is 0b110.

Example 4:

Input: 8
Output: 0
Explanation: 
8 in binary is 0b1000.
There aren't any consecutive pairs of 1's in the binary representation of 8, so we return 0.

Note:

• 1 <= N <= 10^9

题目地址

讲解

首先必定要理解题目的意思，题目的意思是两个连续1之间的最大距离，好比11，最大距离是1，10001最大距离是4.

而后简单的作法是，记录每一个1的坐标，而后算最大的差值。但这样要额外扫描一遍坐标数组。

个人代码作到了只扫描一遍N，须要三个值进行记录，index记录是否扫描到1，count记录每一段1的距离，max记录最大距离。

Java代码

class Solution {
    public int binaryGap(int N) {
        int index=0;
        int count=0;
        int max=0;
        int temp = N;
        while(temp>0){
            if(temp%2==1){
                if(index==1){
                    count++;
                    max = max<count?count:max;
                    count=0;
                }else{
                    index = 1;
                }
            }else{
                if(index==1){
                    count++;
                    max = max<count?count:max;
                }
            }
            temp >>= 1;
            
        }
        return max;
    }
}