Added problems: 3 - Longest Substring Without Repeating Characters

Author: thegovyadina

README.md

@@ -33,6 +33,7 @@ Note that this license applies only to my solution code and not to the LeetCode
 | Problem                                                                                                                                                            |                                        Solution                                         | Approach                           |
 |:-------------------------------------------------------------------------------------------------------------------------------------------------------------------|:---------------------------------------------------------------------------------------:|:-----------------------------------|
 | 🟢 1. [Two Sum](https://leetcode.com/problems/two-sum/)                                                                                                            |                           [🦀](src/problems/p0001_two_sum.rs)                           | Hash Map                           |
+| 🟠 3. [Longest Substring Without Repeating Characters](https://leetcode.com/problems/longest-substring-without-repeating-characters/)                              |       [🦀](src/problems/p0003_longest_substring_without_repeating_characters.rs)        | HashMap, Two Pointers              |
 | 🟢 13. [Roman to Integer](https://leetcode.com/problems/roman-to-integer/)                                                                                         |                      [🦀](src/problems/p0013_roman_to_integer.rs)                       |                                    |
 | 🟢 20. [Valid Parentheses](https://leetcode.com/problems/valid-parentheses/)                                                                                       |                      [🦀](src/problems/p0020_valid_parentheses.rs)                      | Stack                              |
 | 🟢 21. [Merge Two Sorted Lists](https://leetcode.com/problems/merge-two-sorted-lists/)                                                                             |                   [🦀](src/problems/p0021_merge_two_sorted_lists.rs)                    |                                    |

src/problems/mod.rs

@@ -1,4 +1,5 @@
 pub mod p0001_two_sum;
+pub mod p0003_longest_substring_without_repeating_characters;
 pub mod p0013_roman_to_integer;
 pub mod p0020_valid_parentheses;
 pub mod p0021_merge_two_sorted_lists;

src/problems/p0003_longest_substring_without_repeating_characters.rs

@@ -0,0 +1,51 @@
+//! # LeetCode Problem: 3 - Longest Substring Without Repeating Characters
+//!
+//! Difficulty: Medium
+//!
+//! Link: https://leetcode.com/problems/longest-substring-without-repeating-characters/
+//!
+//! ## Complexity Analysis
+//! - Time Complexity: O(n) - We traverse the string containing n characters exactly once.
+//! - Space Complexity: O(n) - The extra space required depends on the number of items
+//!   stored in the hash table.
+
+pub struct Solution;
+
+impl Solution {
+    pub fn length_of_longest_substring(s: String) -> i32 {
+        if s.len() <= 1 {
+            return s.len() as i32;
+        }
+
+        let mut result = 0;
+        let mut left = 0;
+        let mut letters = std::collections::HashMap::new();
+
+        for (right, c) in s.chars().enumerate() {
+            if let Some(&prev_idx) = letters.get(&c) {
+                left = std::cmp::max(prev_idx + 1, left);
+            }
+            letters.insert(c, right);
+            result = std::cmp::max(result, (right - left + 1) as i32);
+        }
+
+        result
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::Solution;
+
+    #[test]
+    fn test_length_of_longest_substring() {
+        let test_cases = [("abcabcbb", 3), ("bbbbb", 1), ("pwwkew", 3)];
+        for (idx, (input, expected)) in test_cases.iter().enumerate() {
+            let result = Solution::length_of_longest_substring(input.to_string());
+            assert_eq!(
+                result, *expected,
+                "Test case #{idx}: with input {input:?}, expected {expected:?}, got {result:?}"
+            );
+        }
+    }
+}