leetcode-3-longest-substring-without-repeating-characters

Description

Given a string, find the length of the longest substring without repeating characters.

Example 1:

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2
3

Input: "abcabcbb"
Output: 3 
Explanation: The answer is "abc", with the length of 3.

Example 2:

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2
3

Input: "bbbbb"
Output: 1
Explanation: The answer is "b", with the length of 1.

Example 3:

Input: "pwwkew"
Output: 3
Explanation: The answer is "wke", with the length of 3. 
             Note that the answer must be a substring, "pwke" is a subsequence and not a substring.

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import java.util.HashMap;
public class Solution {
    public int lengthOfLongestSubstring(String s) {
        if(s == null || s.length() == 0) return 0;
        //新建一个map进行存储char
        HashMap<Character,Integer> map = new HashMap<Character,Integer>();
        int leftBound = 0;
        int max = 0;
        for(int i=0; i<s.length();i++){
            char  c = s.charAt(i);
            //窗口左边可能为下一个char，或者不变
            leftBound = Math.max(leftBound,(map.containsKey(c))? map.get(c)+1:0);
            max = Math.max(max, i-leftBound+1);//当前窗口长度
            map.put(c,i);
        }
        return max;
         
    }
}