Matching substring in the same place on two different strings?

Question

I have been trying to solve one of the codingbat problem in Python.

Here is the problem definition:

Given 2 strings, a and b, return the number of the positions where they contain the same length 2 substring. So "xxcaazz" and "xxbaaz" yields 3, since the "xx", "aa", and "az" substrings appear in the same place in both strings.

string_match('xxcaazz', 'xxbaaz') → 3

string_match('abc', 'abc') → 2

string_match('abc', 'axc') → 0

Here is my code for it:

def string_match(a, b):
  count = 0
  for i in range(len(a)-1):
    for j in range(len(b)-1):
      if a[i:i+2] == b[j:j+2]:
        count += 1
  return count

The output from Above code:

I could not figure out what is wrong with my code.

Hope you can help me out. Looking forward for the response.

Answer 1

This should do the work, passed all your test cases.

def string_match(a, b):
    found = 0
    for i in range(min([len(a), len(b)])-1):
        if a[i] == b[i] and a[i+1] == b[i+1]:
            found += 1
    return found

print(string_match('iaxxai', 'aaxxaaxx'))

You dont need to split the string, you only need to check if the chars at i and i + 1 are equal. If you would like to check it for n length, you might need an inner loop. Also it works for len(a) != len(b) .

Answer 2

def string_match(a, b): shorter = min(len(a), len(b)) count = 0 for i in range(shorter-1): a_sub = a[i:i+2] b_sub = b[i:i+2] if a_sub == b_sub: count = count + 1 return count