LeetCode 1684. Count the Number of Consistent Strings



You are given a string allowed consisting of distinct characters and an array of strings words. A string is consistent if all characters in the string appear in the string allowed.

Return the number of consistent strings in the array words.

Example 1:

Input: allowed = "ab", words = ["ad","bd","aaab","baa","badab"]
Output: 2
Explanation: Strings "aaab" and "baa" are consistent since they only contain characters 'a' and 'b'.

Example 2:

Input: allowed = "abc", words = ["a","b","c","ab","ac","bc","abc"]
Output: 7
Explanation: All strings are consistent.

Example 3:

Input: allowed = "cad", words = ["cc","acd","b","ba","bac","bad","ac","d"]
Output: 4
Explanation: Strings "cc", "acd", "ac", and "d" are consistent.


  • 1 <= words.length <= 104
  • 1 <= allowed.length <=26
  • 1 <= words[i].length <= 10
  • The characters in allowed are distinct.
  • words[i] and allowed contain only lowercase English letters.


Check if all characters are in allowed set.

Python Solution

class Solution:
    def countConsistentStrings(self, allowed: str, words: List[str]) -> int:
        count = 0
        allowed = set(allowed)

        for word in words:
            i = 0
            while i < len(word):
                if word[i] not in allowed:
                i += 1
            if i == len(word): 
                count += 1
        return count
  • Time Complexity: O(N)
  • Space Complexity: O(N)

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