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1876. Substrings of Size Three with Distinct Characters

Easy

A string is good if there are no repeated characters.

Given a string s​​​​​, return the number of good substrings of length three in s​​​​​​.

Note that if there are multiple occurrences of the same substring, every occurrence should be counted.

A substring is a contiguous sequence of characters in a string.

Example 1:

Input: s = "xyzzaz"
Output: 1
Explanation: There are 4 substrings of size 3: "xyz", "yzz", "zza", and "zaz". 
The only good substring of length 3 is "xyz".

Example 2:

Input: s = "aababcabc"
Output: 4
Explanation: There are 7 substrings of size 3: "aab", "aba", "bab", "abc", "bca", "cab", and "abc".
The good substrings are "abc", "bca", "cab", and "abc".

Constraints:

  • 1 <= s.length <= 100
  • s​​​​​​ consists of lowercase English letters.

Solution

class Solution:
    def countGoodSubstrings(self, s: str) -> int:
        count = 0

        for a, b, c in zip(s, s[1:], s[2:]):
            if a != b and a != c and b != c:
                count += 1

        return count