What is the approach to find the longest substring without repeating characters?
This problem asks for the length of the longest substring that contains no duplicate characters. It tests sliding window and hash map techniques.
Why Interviewers Ask This
Interviewers use this to assess sliding window pattern recognition and character tracking skills. They want to see if you can dynamically adjust the window size based on duplicate detection. It demonstrates efficient string processing and state management.
How to Answer This Question
Explain the sliding window concept where the window expands by moving the right pointer and contracts by moving the left pointer upon finding duplicates. Use a hash map or array to store the last seen index of each character. When a duplicate is found, jump the left pointer to the position after the previous occurrence. Track the maximum window size encountered.
Key Points to Cover
- Sliding window expansion and contraction
- Last seen index tracking
- Dynamic left pointer movement
- Single pass efficiency
Sample Answer
I would use a sliding window approach with a hash map to store the last index of each character. I maintain a left pointer and a right pointer. As I expand the window with the right pointer, I check if the current charac…
Common Mistakes to Avoid
- Moving left pointer one step at a time instead of jumping
- Not checking if the duplicate is within the current window
- Using a set instead of a map for index tracking
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