1876. Substrings of Size Three with Distinct Characters【字符串】

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.

题意：如果一个字符串不含有任何重复字符，我们称这个字符串为 好 字符串。

给你一个字符串 s ，请你返回 s 中长度为 3 的 好子字符串 的数量。注意，如果相同的好子字符串出现多次，每一次都应该被记入答案之中。

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解法 字符串

遍历字符串，每次取三个连续的字符，只要都不相等，就计算一次。

class Solution {
public:
    int countGoodSubstrings(string s) { 
        int ans = 0;
        for (int i = 0, n = s.size(); i <= n - 3; ++i)
            if (s[i] != s[i + 1] && s[i] != s[i + 2] && s[i + 1] != s[i + 2]) ++ans;
        return ans;
    }
};

运行效率如下：

执行用时：0 ms, 在所有 C++ 提交中击败了100.00% 的用户
内存消耗：6.1 MB, 在所有 C++ 提交中击败了20.00% 的用户