Subpalindrome

subpalindrome.py

# --------------
# User Instructions
#
# Write a function, longest_subpalindrome_slice(text) that takes
# a string as input and returns the i and j indices that
# correspond to the beginning and end indices of the longest
# palindrome in the string.
#
# Grading Notes:
#
# You will only be marked correct if your function runs
# efficiently enough. We will be measuring efficency by counting
# the number of times you access each string. That count must be
# below a certain threshold to be marked correct.
#
# Please do not use regular expressions to solve this quiz!

def longest_subpalindrome_slice(text):
    "Return (i, j) such that text[i:j] is the longest palindrome in text."
    length = len(text)
    text = text.lower()

    return max([(i, j) for i in range(length + 1) for j in range(i, length + 1) if text[i:j] == text[i:j][::-1]], key=lambda x: abs(x[0] - x[1]))

def test():
    L = longest_subpalindrome_slice
    assert L('racecar') == (0, 7)
    assert L('Racecar') == (0, 7)
    assert L('RacecarX') == (0, 7)
    assert L('Race carr') == (7, 9)
    assert L('') == (0, 0)
    assert L('something rac e car going') == (8,21)
    assert L('xxxxx') == (0, 5)
    assert L('Mad am I ma dam.') == (0, 15)
    return 'tests pass'

test()