Substrings of Size Three with Distinct Characters

Problem

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 (Java)

class Solution {
    public int countGoodSubstrings(String s) {
        int count = 0;
        for (int i = 0; i < s.length() - 2; i++) {
            String candidate = s.substring(i, i + 3);
            if (candidate.charAt(0) != candidate.charAt(1)
                    && candidate.charAt(0) != candidate.charAt(2)
                    && candidate.charAt(1) != candidate.charAt(2)) {
                count++;
            }
        }
        return count;
    }
}

Explain:

nope.

Complexity:

Time complexity : O(n).
Space complexity : O(n).