Longest Common Prefix of K Strings After Removal

Problem Description

You are given an array of strings words and an integer k. For each index i in the range [0, words.length - 1], find the length of the longest common prefix among any k strings (selected at distinct indices) from the remaining array after removing the ith element. Return an array answer, where answer[i] is the answer for ith element. If removing the ith element leaves the array with fewer than k strings, answer[i] is 0.

Key Insights

• The problem requires calculating the longest common prefix after removing each string from the array.
• If there are fewer than k strings remaining after removal, the result is 0.
• To efficiently compute the longest common prefix among k strings, we can leverage sorting or a frequency-based approach.
• The use of data structures like a Trie can help manage and compare prefixes across multiple strings.

Space and Time Complexity

Time Complexity: O(n * m * log m), where n is the number of strings and m is the maximum length of the strings, due to sorting. Space Complexity: O(n * m) for storing the strings and any auxiliary data structures.

Solution

To solve the problem, we will:

1. For each index i, remove the string at that index and check the remaining strings.
2. If the remaining strings are fewer than k, return 0 for that index.
3. Otherwise, count the occurrences of each string using a frequency map.
4. Determine the longest common prefix from the k most frequent strings.
5. Store the result in the answer array.

Code Solutions