Leetcode: longest-substring-without-repeating-characters

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题目：

Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the length is 3. For "bbbbb" the longest substring is "b", with the length of 1.

思路：

1.利用HashMap保存字符及所在位置信息。

2.设置滑动窗口向右滑动，每当新加一个char时，左边检查窗口内是否重复

3.重复的话就将窗口左边放置在该字符上次出现的下一位

4.记录过程中窗口最大值、

代码：

import java.util.*;public class Solution {    public int lengthOfLongestSubstring(String s) {        if(s==null || s.length()==0)            return 0;        HashMap<Character,Integer> map = new HashMap<Character,Integer>();        int left = 0; //窗口左边位置        int max = 0;        for(int i=0; i<s.length(); i++)        {            char c = s.charAt(i);            left = Math.max(left, map.containsKey(c)?map.get(c)+1:0);            max = Math.max(max, i-left+1);            map.put(c, i);        }        return max;    }}

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