Question

Does anyone have an English explanation? (sorry)


Problem 4. Write a function, called which takes two arguments: a target string and a key string. This function should return a tuple of all starting points of matches of the key to the target, such that at exactly one element of the key is incorrectly matched to the target. Complete the definition

Answer 1

Consider case target: atgacatgcacaagtatgcat and key: atgc.

In problem 3, we want to return starting points for matches with up to one substitution (i.e. zero or one). So we would return 5, for the case of zero substitutions since it identically matches the target. And we would get 0, for the case of one substitution, 'a' in place of 'c'.

Problem 4 is asking for only the starting points of the latter situation. It wants you to return starting points strictly for matches with one substitution.