What is the strategy to find the largest word by deleting characters?
The task requires finding the longest dictionary word that can be formed by deleting zero or more characters from a given source string. This tests string matching and greedy approaches.
Why Interviewers Ask This
This question assesses a candidate's ability to implement efficient string matching algorithms. Interviewers want to see if the candidate can avoid brute-force substring generation and instead use a two-pointer or greedy strategy. It also evaluates understanding of lexicographical ordering when multiple words have the same maximum length.
How to Answer This Question
Propose iterating through the dictionary words and checking if each can be formed as a subsequence of the source string. Use a two-pointer approach to verify the subsequence property in linear time relative to the string lengths. If multiple words have the same length, compare them lexicographically to pick the correct one. Highlight the efficiency of this approach compared to generating all subsequences.
Key Points to Cover
- Check subsequence property using two pointers
- Filter dictionary words based on validity
- Select the longest valid word
- Resolve ties using lexicographical comparison
Sample Answer
I would iterate through each word in the dictionary and check if it is a subsequence of the source string. To do this efficiently, I use two pointers: one for the source string and one for the dictionary word. If characters match, I advance both; otherwise, I advance only the source pointer. If I reach the end of the dictionary word, it is a valid candidate. Among all valid candidates, I select the longest one, breaking ties lexicographically.
Common Mistakes to Avoid
- Generating all subsequences unnecessarily
- Incorrectly comparing words of equal length
- Failing to handle case sensitivity or special characters
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