1876. Substrings of Size Three with Distinct Characters

Problem

Tags: Hash Table, String, Sliding Window, Counting

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.

Code

JS

// 1876. Substrings of Size Three with Distinct Characters (8/13/53378)
// Runtime: 140 ms (3.27%) Memory: 39.62 MB (94.86%) 

/**
 * @param {string} s
 * @return {number}
 */
var countGoodSubstrings = function(s) {
    let solution = 0;
    for(var i = 0; i < s.length - 2; i++) {
        let sub = s.substr(i, 3);
        if(good(sub)) solution++;
    }
    return solution;
};

function good(str) {
    if(str[0] != str[1] && str[1] != str[2] && str[0] != str[2]) return true;
    else return false;
}