# [LeetCode]#1876. Substrings of Size Three with Distinct Characters

**Environment: Python 3.8**

**Key technique: for, if, !=**

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".

**Analysis:**

- if s[i] != s[i+1] and s[i] != s[i+2] and s[i+1] !=s[i+2], ans+=1.
- Return ans

**Solution:**

`class Solution:`

def countGoodSubstrings(self, s):

ans=0

for i in range(len(s)-2):

if (s[i] != s[i+1] and s[i] != s[i+2] and s[i+1] !=s[i+2]):

ans+=1

return ans

**Submissions:**