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.

1876. Substrings of Size Three with Distinct Characters
struct Solution;

impl Solution {
    fn count_good_substrings(s: String) -> i32 {
        let s: Vec<char> = s.chars().collect();
        let n = s.len();
        let mut res = 0;
        for i in 2..n {
            if s[i] != s[i - 1] && s[i] != s[i - 2] && s[i - 1] != s[i - 2] {
                res += 1;
            }
        }
        res
    }
}

#[test]
fn test() {
    let s = "xyzzaz".to_string();
    let res = 1;
    assert_eq!(Solution::count_good_substrings(s), res);
    let s = "aababcabc".to_string();
    let res = 4;
    assert_eq!(Solution::count_good_substrings(s), res);
}