Add Longest Substring Without Repeating Characters

Author: thanthtooaung-coding

Longest Substring Without Repeating Characters/README.md

@@ -0,0 +1,42 @@
+# Longest Substring Without Repeating Characters
+
+## LeetCode Problem
+- Problem Number: 3
+- Problem Link: https://leetcode.com/problems/longest-substring-without-repeating-characters/
+- Difficulty: Medium
+- Topics: Hash Table, String, Sliding Window
+
+## Problem Description
+Given a string s, find the length of the longest substring without repeating characters.
+
+Note:
+- A substring is a contiguous sequence of characters within the string
+- The substring must not have any repeating characters
+
+## Examples
+
+### 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 * 10⁴
+- s consists of English letters, digits, symbols and spaces

Longest Substring Without Repeating Characters/Solution.java

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+import java.util.HashSet;
+
+class Solution {
+    public int lengthOfLongestSubstring(String s) {
+        if (s == null || s.length() == 0) {
+            return 0;
+        }
+
+        HashSet<Character> set = new HashSet<>();
+        int maxLen = 0;
+        int left = 0;
+
+        for (int right = 0; right < s.length(); right++) {
+            char currentChar = s.charAt(right);
+
+            while (set.contains(currentChar)) {
+                set.remove(s.charAt(left));
+                left++;
+            }
+
+            set.add(currentChar);
+
+            maxLen = Math.max(maxLen, right - left + 1);
+        }
+
+        return maxLen;
+    }
+}

README.md

@@ -14,14 +14,15 @@ Each problem has its own directory containing:
 |---|-------|------------|----------|---------|
 | 1 | [Two Sum](Two%20Sum) | Easy | [Java](Two%20Sum/Solution.java) | Array, Hash Table |
 | 2 | [Add Two Numbers](Add%20Two%20Numbers) | Medium | [Java](Add%20Two%20Numbers/Solution.java) | Linked List, Math, Recursion |
+| 3 | [Longest Substring Without Repeating Characters](Longest%20Substring%20Without%20Repeating%20Characters) | Medium | [Java](Longest%20Substring%20Without%20Repeating%20Characters/Solution.java) | Hash Table, String, Sliding Window |
 | 4 | [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays) | Hard | [Java](Median%20of%20Two%20Sorted%20Arrays/Solution.java) | Array, Binary Search, Divide and Conquer |
 | 2924 | [Find Champion II](Find%20Champion%20II) | Medium | [Java](Find%20Champion%20II/Solution.java) | Graph |
 
 ## Categories
 
 ### By Difficulty
 - Easy: 1
-- Medium: 2
+- Medium: 3
 - Hard: 1
 
 ### By Topics
@@ -30,6 +31,9 @@ Each problem has its own directory containing:
   - [Median of Two Sorted Arrays](Median%20of%20Two%20Sorted%20Arrays)
 - Hash Table Problems
   - [Two Sum](Two%20Sum)
+  - [Longest Substring Without Repeating Characters](Longest%20Substring%20Without%20Repeating%20Characters)
+- String Problems
+  - [Longest Substring Without Repeating Characters](Longest%20Substring%20Without%20Repeating%20Characters)
 - Linked List Problems
   - [Add Two Numbers](Add%20Two%20Numbers)
 - Math Problems