substring_search.py

# Recursive Python3 program to find if a given pattern is
# present in a text


def exactMatch(text, pat, text_index, pat_index):
    if text_index == len(text) and pat_index != len(pat):
        return 0

    # Else If last character of pattern reaches
    if pat_index == len(pat):
        return 1

    if text[text_index] == pat[pat_index]:
        return exactMatch(text, pat, text_index + 1, pat_index + 1)

    return 0


# This function returns true if 'text' contain 'pat'
def contains(text, pat, text_index, pat_index):
    # If last character of text reaches
    if text_index == len(text):
        return 0

    # If current characters of pat and text match
    if text[text_index] == pat[pat_index]:
        if exactMatch(text, pat, text_index, pat_index):
            return 1
        else:
            return contains(text, pat, text_index + 1, pat_index)

        # If current characters of pat and tex don't match
    return contains(text, pat, text_index + 1, pat_index)


# Driver program to test the above function

print(contains("geeksforgeeks", "geeks", 0, 0))
print(contains("geeksforgeeks", "geeksquiz", 0, 0))
print(contains("geeksquizgeeks", "quiz", 0, 0))