Longest Substring Without Repeating Characters

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

Example 1:

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

Example 2:

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.s

time space o(n), o(n)

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