Longest Substring Without Repeating Characters

In this article we will learn about LeetCode Third question Longest Substring Without Repeating Characters in detail with optimized solution with Example.

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

Table of Contents

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.

Constraints:

0 <= s.length <= 5 * 10<sup>4</sup>
s consists of English letters, digits, symbols and spaces.

Java Example

class Solution {
    public int lengthOfLongestSubstring(String s) {

        int l=0,r=0;
        Set<Character> seen = new HashSet();
        int max=0;

        while(r< s.length()){
            char c= s.charAt(r);
            if(seen.add(c)){
                max= Math.max(max,r-l+1);
                r++;
            }else{
                while(s.charAt(l)!=c){
                    seen.remove(s.charAt(l));
                    l++;
                }
           seen.remove(c);
           l++;
            }
        } 
     return max;   
    }
}
// 2023

Complexity :

Time complexity: O(N);
Space Complexity: O(1);

I hope you like this Amazing Longest Substring article.🙂