Initial commit

Author: raphaelkw

longest_substring_with_k_distinct_characters_grok.py

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+# Longest Substring with K Distinct Characters (medium)
+# Given a string, find the length of the longest substring in it with no more than K distinct characters.
+# You can assume that K is less than or equal to the length of the given string.
+
+# Input: String="araaci", K=2
+# Output: 4
+# Explanation: The longest substring with no more than '2' distinct characters is "araa".
+
+def longest_substring_with_k_distinct(str1, k):
+  window_start = 0
+  max_length = 0
+  char_frequency = {}
+
+  # in the following loop we'll 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 char_frequency:
+      char_frequency[right_char] = 0
+    char_frequency[right_char] += 1
+
+    # shrink the sliding window, until we are left with 'k' distinct characters in the char_frequency
+    while len(char_frequency) > k:
+      left_char = str1[window_start]
+      char_frequency[left_char] -= 1
+      if char_frequency[left_char] == 0:
+        del char_frequency[left_char]
+      window_start += 1  # shrink the window
+    # remember the maximum length so far
+    max_length = max(max_length, window_end-window_start + 1)
+  return max_length
+
+
+def main():
+  print("Length of the longest substring: " + str(longest_substring_with_k_distinct("araaci", 2))) # 4 
+  print("Length of the longest substring: " + str(longest_substring_with_k_distinct("araaci", 1))) # 2
+  print("Length of the longest substring: " + str(longest_substring_with_k_distinct("cbbebi", 3))) # 5
+
+
+main()