Longest Word in Dictionary through Deleting - Solution & Explanation

This approach involves using a two-pointer technique to check if a string from the dictionary is a subsequence of the given string s. We iterate through each word in the dictionary and for each word, use two pointers to traverse through the word and s. If all characters of the word are found in the same order in s, then it's a valid word. We maintain a result variable to track the longest valid word found so far, and if multiple are of the same length, we track the smallest lexicographical order.

The solution defines a helper function isSubsequence that determines if a given word is a subsequence of s by using two pointers: one traversing s and the other traversing the word. The main logic iterates through each word in the dictionary and checks if it is a subsequence, updating the result if it is longer or lexicographically smaller than the previous result.

This approach involves sorting the dictionary by length (descending) and lexicographical order (ascending). By sorting first, you can ensure that you are checking the longest available words first while resolving ties based on the smallest alphabetical order. We then iterate through this sorted list and use a function to check if a word is a valid subsequence of s.

This Python implementation uses sorting to align words by the desirable evaluation order: first longest, then smallest lexicographically. The `is_subsequence` function checks if a word is a subsequence of `s`, as before accomplished using iterators for efficiency.