无重复字符的最长子串

Algorithm

3. Longest Substring Without Repeating Characters

Description

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

Example 1:

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

Example 2:

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

Example 3:

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

Example 4:

Input: s = ""
Output: 0

Constraints:

• 0 <= s.length <= 5 * 104
• s consists of English letters, digits, symbols and spaces.

Solution

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

Code

3. Longest Substring Without Repeating Characters