This approach involves sorting the words array. By sorting, words that could potentially be built upon would appear earlier in the list. After sorting, we use a set to keep track of words that can be built character by character.

The process is as follows:

1. Sort the words array first based on length, then lexicographically.
2. Initialize a set with an empty string.
3. Iterate through each word in the sorted array:
• Check if the prefix of the word (without the last character) exists in the set.
• If it exists, add the whole word to the set.
4. Track the longest word found during the iteration.

This is efficient due to the pre-sorting which allows easy checking and ensures we are building words correctly by the constraints given.

This approach uses a Trie (prefix tree) to store the words. By utilizing this data structure, we aim to verify if a word can be constructed by progressively building on its prefixes.

The steps are:

1. Build a Trie from the words array.
2. For each word, check if all its prefixes are present in the Trie.
3. Track the longest word that meets the criterion.
4. If multiple words have the same length, select the lexicographically smallest one.

This combines efficient storage and lookup, with Prefix trees naturally lending themselves to this problem due to their structure.