Longest Word in Dictionary
The problem is to find the longest word in a given dictionary that can be constructed one character at a time by other words in the dictionary. If there are multiple words of the same length, we need to return the one that comes first lexicographically.
Here’s a stepbystep guide to solve this problem:
1. Sort the words and add them to a set
First, we sort the words so that we deal with shorter words first, and add all words to a set for quick lookup.
2. Check each word
Iterate through the sorted words and check if each prefix of the word exists in the set. We can use a variable to keep track of the current longest word that can be constructed.
3. Return the result
Return the longest word that can be constructed.
Code


Insights
 Sorting: Sorting ensures that shorter words are considered first, so they can act as building blocks for longer words.
 Prefix Checking: By checking all prefixes of a word, we ensure that it can be constructed one character at a time.
 Lexicographical Order: Since the words are sorted, we naturally consider lexicographically smaller words first.
 Time Complexity: Sorting the words takes (O(n \log n)) time, where (n) is the total number of characters across all words. Checking prefixes takes (O(n)) time. So, the overall time complexity is (O(n \log n)).
 Space Complexity: Storing the words in a set takes (O(n)) space.
This solution efficiently finds the longest word that can be constructed from other words in the dictionary, considering both length and lexicographical order.


title: Longest Word in Dictionary excerpt: Checking prefixes to construct the longest word in Dictionary tags: prefix
Solution
I modified the solution that I found online to make it easier to follow the tracing of calls in a debugger. The code is concise and elegant.


Run this through the debugger to understand how to code works.