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.

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

Runtime: 7 ms, faster than 82.37% of Java online submissions for Longest Substring Without Repeating Characters.

Memory Usage: 36 MB, less than 100.00% of Java online submissions for Longest Substring Without Repeating Characters.