Can you explain how 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. It tests string matching and greedy approaches.
Why Interviewers Ask This
This question checks a candidate's ability to implement efficient string matching algorithms. It evaluates logical thinking regarding subsequence problems and the trade-off between checking every dictionary word versus optimizing the search.
How to Answer This Question
Propose iterating through the dictionary and checking if each word is a subsequence of the source string. Use a two-pointer technique for the subsequence check. Sort the dictionary by length descending to return the first match found. Discuss time complexity relative to dictionary size and string lengths.
Key Points to Cover
- Check if dictionary words are subsequences of the source
- Use two-pointer technique for efficient matching
- Sort dictionary by length to optimize return
- Handle empty or non-matching cases gracefully
Sample Answer
I would iterate through the dictionary words, prioritizing longer ones. For each word, I check if it is a subsequence of the source string using two pointers. One pointer tracks the source string, the other the dictionary word. If the characters match, I advance both; otherwise, only the source pointer moves. If I reach the end of the dictionary word, it is a valid match. Sorting the dictionary ensures I return the largest valid word first.
Common Mistakes to Avoid
- Checking all permutations instead of subsequences
- Ignoring the need to sort by length
- Inefficiently scanning the source string repeatedly
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