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This is an interview question: Find all (english word) substrings of a given string. (every = every, ever, very).
Obviously, we can loop over all substrings and check each one against an English dictionary, organized as a set. I believe the dictionary is small enough to fit the RAM. How to organize the dictionary ? As for as I remember, the original spell command loaded the words file in a bitmap, represented a set of words hash values. I would start from that.
Another solution is a trie built from the dictionary. Using the trie we can loop over all string characters and check the trie for each character. I guess the complexity of this solution would be the same in the worst case (O(n^2))
Does it make sense? Would you suggest other solutions?
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If the length of a string is N, then there can be N – K + 1 substring of length K. Generating these substrings will require O(N) complexity, and checking each substring requires O(K) complexity, hence making the overall complexity like O(N*K). Efficient approach: The idea is to use Window Sliding Technique.
The function strstr returns the first occurrence of a string in another string. This means that strstr can be used to detect whether a string contains another string. In other words, whether a string is a substring of another string.
A substring is a subset or part of another string, or it is a contiguous sequence of characters within a string.
The Aho-Corasick string matching algorithm which "constructs a finite state machine that resembles a trie with additional links between the various internal nodes."
But everything considered the "build a trie from the English dictionary and do a simultaneous search on it for all suffixes of the given string" should be pretty good for an interview.
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