longest substring code

long_sub_str.py

def length_of_longest_substring(str1, k):
  window_start, max_length, max_repeat_letter_count = 0, 0, 0

  frequency_map = {}

  # Try to extend the range [window_start, window_end]
	for window_end in range(len(str1)):
    right_char = str1[window_end]

    if right_char not in frequency_map:
      frequency_map[right_char] = 0

    frequency_map[right_char] += 1

    max_repeat_letter_count = max(
      max_repeat_letter_count, frequency_map[right_char])

    # Current window size is from window_start to window_end, overall we have a letter which is
    # repeating 'max_repeat_letter_count' times, this means we can have a window which has one letter
    # repeating 'max_repeat_letter_count' times and the remaining letters we should replace.
    # if the remaining letters are more than 'k', it is the time to shrink the window as we
    # are not allowed to replace more than 'k' letters
    
   current_length = window_end - window_start + 1
   
	 if (current_length - max_repeat_letter_count) > k:
      left_char = str1[window_start]
      frequency_map[left_char] -= 1
      window_start += 1

    max_length = max(max_length, current_length)

  return max_length

def main():
  print(length_of_longest_substring("aabccbb", 2))
  print(length_of_longest_substring("abbcb", 1))
  print(length_of_longest_substring("abccde", 1))

main()