LeetCode:Longest Substring Without Repeating Characters

Longest Substring Without Repeating Characters

Total Accepted: 152787  Total Submissions: 687012  Difficulty: Medium

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

Examples:

Given "abcabcbb", the answer is "abc", which the length is 3.

Given "bbbbb", the answer is "b", with the length of 1.

Given "pwwkew", 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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  Hash Table Two Pointers String

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  (H) Longest Substring with At Most Two Distinct Characters

思路：

维护一个HashMap存储每个字符的位置；两个指针i,j，维护最长子串的范围。

java code:

public class Solution {
    public int lengthOfLongestSubstring(String s) {
        
        if(s==null || s.length()==0) return 0;
        Map<Character, Integer> map = new HashMap<Character, Integer>();
        int max = 0;
        for(int i=0,j=0;i<s.length();i++) {
            char c = s.charAt(i);
            if(map.containsKey(c)) {
                j = Math.max(j, map.get(c)+1);
            }
            map.put(c, i);
            max = Math.max(max, i-j+1);
        }
        return max;
    }
}