Is Longest Word in Dictionary through Deleting easy or hard?

The problem is rated Medium on LeetCode because it combines multiple ideas: subsequence detection, lexicographic ordering, and careful candidate selection. The implementation is straightforward once you recognize the two-pointer subsequence pattern.

Longest Word in Dictionary through Deleting Python/Java solution

In Python or Java, iterate through each dictionary word and check if it is a subsequence of the string using two indices. Update the best candidate when a longer word is found or when the length is equal but the word is lexicographically smaller. This approach keeps the implementation short and runs in O(D * n) time.

How to solve Longest Word in Dictionary through Deleting in O(n)?

The subsequence check itself runs in O(n) time for a single candidate word using two pointers. One pointer scans the main string while the other scans the dictionary word. In practice, the full problem runs in O(D * n) because the subsequence test must be repeated for multiple dictionary entries.

What is the best approach for Longest Word in Dictionary through Deleting?

The most practical solution uses a two-pointer subsequence check. For each word in the dictionary, scan the main string with one pointer and advance the second pointer when characters match. If the dictionary pointer reaches the end, the word is a valid subsequence. This runs in O(D * |s|) time and O(1) space.

Is Longest Word in Dictionary through Deleting asked at Google/Amazon/Meta?

Variants of subsequence checking and dictionary filtering appear in interviews at companies like Google, Amazon, and Meta. The problem tests string traversal, lexicographic comparison, and efficient scanning using two pointers, which are common interview patterns.

What data structure is used in Longest Word in Dictionary through Deleting?

The core data structures are arrays or lists for the dictionary and simple string traversal with two pointers. Some implementations also use sorting on the dictionary to prioritize longer or lexicographically smaller words before performing subsequence checks.

What is the time complexity of Longest Word in Dictionary through Deleting?

Using the two-pointer approach, each dictionary word requires a linear scan of the string. If the dictionary has D words and the string length is n, the total time complexity is O(D * n). If the dictionary is sorted first to prioritize longer words, an additional O(D log D) sorting cost is added.

524. Longest Word in Dictionary through Deleting - Practice Online

Given a string s and a string array dictionary, return the longest string in the dictionary that can be formed by deleting some of the given string characters. If there is more than one possible result, return the longest word with the smallest lexicographical order. If there is no possible result, return the empty string.

Example 1:

Input: s = "abpcplea", dictionary = ["ale","apple","monkey","plea"]
Output: "apple"

Example 2:

Input: s = "abpcplea", dictionary = ["a","b","c"]
Output: "a"

Constraints:

1 <= s.length <= 1000
1 <= dictionary.length <= 1000
1 <= dictionary[i].length <= 1000
s and dictionary[i] consist of lowercase English letters.