solves longestsubstring with repeating characters

Author: anishLearnsToCode

README.md

@@ -13,6 +13,7 @@
 |:----:|-----------------------------------------------------------------------------------------------------------------------------------------------------------|:------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------:|:---------------------------------------------------------------------------------------------------------------------------------:|
 |  1   | [Two Sum](https://leetcode.com/problems/two-sum/)                                                                                                         |                                            [![Java](assets/java.png)](src/TwoSum.java) [![Python](assets/python.png)](python/two_sum.py)                                             | [![java-yt](assets/java-yt.png)](https://youtu.be/9wSL_7NN-A8) [![python-yt](assets/python-yt.png)](https://youtu.be/N5FXCTg0TDE) |
 |  2   | [Add Two Numbers](https://leetcode.com/problems/add-two-numbers)                                                                                          |                                                                  [![Java](assets/java.png)](src/AddTwoNumbers.java)                                                                  |                                                                                                                                   |
+|  3   | [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters)                            |                                                   [![Java](assets/java.png)](src/LongestSubstringWithoutRepeatingCharacters.java)                                                    |                                                                                                                                   |
 |  7   | [Reverse Integer](https://leetcode.com/problems/reverse-integer/)                                                                                         |                                    [![Java](assets/java.png)](src/ReverseInteger.java) [![Python](assets/python.png)](python/reverse_integer.py)                                     | [![java-yt](assets/java-yt.png)](https://youtu.be/7bOhyl5lWjI) [![python-yt](assets/python-yt.png)](https://youtu.be/lmLG30TLcSg) |
 |  9   | [PalindromeNumber](https://leetcode.com/problems/palindrome-number/)                                                                                      |                                  [![Java](assets/java.png)](src/PalindromeNumber.java) [![Python](assets/python.png)](python/palindrome_number.py)                                   |                                                                                                                                   |
 |  13  | [Roman To Integer](https://leetcode.com/problems/roman-to-integer/)                                                                                       |                                    [![Java](assets/java.png)](src/RomanToInteger.java) [![Python](assets/python.png)](python/roman_to_integer.py)                                    | [![java-yt](assets/java-yt.png)](https://youtu.be/BCue_mO_81A) [![python-yt](assets/python-yt.png)](https://youtu.be/8h_yGTNvKMA) |

src/LongestSubstringWithoutRepeatingCharacters.java

@@ -0,0 +1,23 @@
+// https://leetcode.com/problems/longest-substring-without-repeating-characters
+// T: O(|s|)
+// S: O(1)
+
+import java.util.HashSet;
+import java.util.Set;
+
+public class LongestSubstringWithoutRepeatingCharacters {
+    public int lengthOfLongestSubstring(String s) {
+        final Set<Character> letters = new HashSet<>();
+        int maxLength = 1;
+        for (int i = 0, j = 0 ; i < s.length() ; i++) {
+            if (letters.contains(s.charAt(i))) {
+                while (letters.contains(s.charAt(i))) {
+                    letters.remove(s.charAt(j++));
+                }
+            }
+            letters.add(s.charAt(i));
+            maxLength = Math.max(maxLength, i - j + 1);
+        }
+        return maxLength;
+    }
+}