How do you find the largest word in a dictionary by deleting characters?
The problem requires finding the longest word in a dictionary that can be formed by deleting zero or more characters from a source string. It tests string traversal and greedy strategies.
Why Interviewers Ask This
This question assesses a candidate's ability to design efficient string comparison algorithms. Interviewers look for a solution better than brute force, often involving sorting or two-pointer techniques. It also evaluates attention to tie-breaking rules like lexicographical order.
How to Answer This Question
Propose a helper function to check if a dictionary word is a subsequence of the source string. Iterate through the dictionary, checking each word against the source. Keep track of the longest valid word found so far, updating it if a longer one is found or if lengths are equal but the new word is lexicographically smaller. Optimize by sorting the dictionary first.
Key Points to Cover
- Sort dictionary to prioritize longest and lexicographically smallest words
- Implement an efficient subsequence check using two pointers
- Return immediately upon finding the first valid match due to sorting
- Handle edge cases like empty dictionaries
Sample Answer
I would first sort the dictionary by length descending and then lexicographically ascending. Then, for each word, I check if it is a subsequence of the source string using a two-pointer approach. The first word that sati…
Common Mistakes to Avoid
- Checking every permutation instead of just subsequences
- Ignoring the lexicographical tie-breaker requirement
- Using inefficient string matching algorithms
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