1876. Substrings of Size Three with Distinct Characters

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.

---

class Solution:
    def countGoodSubstrings(self, s: str) -> int:
        def isvalid(str):
            return False if str[0]==str[1] or str[1] == str[2] or str[0]==str[2] else True

        if len(s)<3:
            return 0
        count=0
        for i in range(len(s)-2):
            count+=isvalid(s[i:i+3])
        return count