Longest Substring Without Repeating Characters

LeetCode 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.

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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