String Search: Brute Force

August 21, 2009

In this exercise, and several that will follow, we will examine algorithms for searching a string. Our goal is to write a function that takes a pattern and a string and either returns the index of the first location of the pattern or an indication that the pattern is not present in the string; an optional third argument allows the search to start at an arbitrary point in the string. Our pattern is simply a fixed string; unlike regular expressions, there are no meta-characters.

Our first string-search algorithm uses brute force: place the pattern at each possible location in the search string and compare character-by-character to determine if there is a match.

Your task is to write a function that performs brute-force string searching as described above. Since we will be writing several other string searching functions, you should also write a test suite that will find any errors in your function. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.

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