MEDIUM NC#16 Blind #50 Sliding Window
3. Longest Substring Without Repeating Characters
📖 Problem
Given a string s, find the length of the longest substring without repeating characters.
🧠 Visual Learning Aid
1 Model the input into the right structure
2 Choose the core technique and invariant
3 Execute step-by-step with a sample
4 Validate complexity and edge cases
JS/TS Refreshers
- •Array methods (`push`, `pop`, `shift`, `slice`)
- •Object/Map/Set usage patterns
- •Function parameter and return typing
- •String/array indexing
- •Set/Map frequency counting
- •Pointer movement invariants
Logical Thinking Concepts
- •Define invariants before coding
- •Check edge cases first (`[]`, single element, duplicates)
- •Estimate time/space before implementation
- •Apply Sliding Window reasoning pattern
- •Apply Two Pointers reasoning pattern
💡 Approach
- → Use sliding window with left and right pointers
- → Use hash map to track last seen index of each character
- → When duplicate found, move left pointer past previous occurrence
- → Track maximum window size
- → Time: O(n), Space: O(min(m, n)) where m is charset size
🧭 Prerequisites
🛠️ Hints & Pitfalls
Hints
- •Use sliding window with left and right pointers
- •Use hash map to track last seen index of each character
- •When duplicate found, move left pointer past previous occurrence
Common Pitfalls
- •Track maximum window size
- •Time: O(n), Space: O(min(m, n)) where m is charset size
🧪 Test Cases
Hidden tests on submit: 3
Test Case 1
Not run Input:
lengthOfLongestSubstring('abcabcbb'); Expected:
3 Test Case 2
Not run Input:
lengthOfLongestSubstring('bbbbb'); Expected:
1 Test Case 3
Not run Input:
lengthOfLongestSubstring('pwwkew'); Expected:
3 📝 Code Editor
📤 Output