1100. Find K-Length Substrings With No Repeated Characters

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1100. Find K-Length Substrings With No Repeated Characters

Description

Given a string s and an integer k, return the number of substrings in s of length k with no repeated characters.

Example 1:

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Input: s = "havefunonleetcode", k = 5
Output: 6
Explanation: There are 6 substrings they are: 'havef','avefu','vefun','efuno','etcod','tcode'.

Example 2:

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Input: s = "home", k = 5
Output: 0
Explanation: Notice k can be larger than the length of s. In this case, it is not possible to find any substring.

Constraints:

  • 1 <= s.length <= 10^4
  • s consists of lowercase English letters.
  • 1 <= k <= 10^4

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Solution

Language: C++

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class Solution {
public:
    int numKLenSubstrNoRepeats(string s, int k) {
        int n = s.size(), right = 0, res = 0, valid = 0;
        vector<int> m(26, 0);
        while (right < n) {
            char c = s[right];
            m[c - 'a']++;
            if (m[c - 'a'] == 1) {
                valid++;
            }
            if (right >= k - 1) {
                if (valid == k) {
                    res++;
                }
                char l = s[right - k + 1];
                m[l - 'a']--;
                if (m[l - 'a'] == 0) {
                    valid--;
                }
            }
            right++;
        }
        return res;
    }
};