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1876. Substrings of Size Three with Distinct Characters

Description

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.

Solutions

• Java
• Python
• TypeScript
• Php
• C++
• Go

• class Solution {
      public int countGoodSubstrings(String s) {
          int count = 0, n = s.length();
          for (int i = 0; i < n - 2; ++i) {
              char a = s.charAt(i), b = s.charAt(i + 1), c = s.charAt(i + 2);
              if (a != b && a != c && b != c) {
                  ++count;
              }
          }
          return count;
      }
  }
  

• class Solution:
      def countGoodSubstrings(self, s: str) -> int:
          count, n = 0, len(s)
          for i in range(n - 2):
              count += s[i] != s[i + 1] and s[i] != s[i + 2] and s[i + 1] != s[i + 2]
          return count
  
  

• function countGoodSubstrings(s: string): number {
      const n: number = s.length;
      let count: number = 0;
      for (let i: number = 0; i < n - 2; ++i) {
          let a: string = s.charAt(i),
              b: string = s.charAt(i + 1),
              c: string = s.charAt(i + 2);
          if (a != b && a != c && b != c) {
              ++count;
          }
      }
      return count;
  }
  
  

• class Solution {
      /**
       * @param String $s
       * @return Integer
       */
      function countGoodSubstrings($s) {
          $cnt = 0;
          for ($i = 0; $i < strlen($s) - 2; $i++) {
              if ($s[$i] != $s[$i + 1] && $s[$i] != $s[$i + 2] && $s[$i + 1] != $s[$i + 2]) {
                  $cnt++;
              }
          }
          return $cnt++;
      }
  }
  
  

• class Solution {
  public:
      int countGoodSubstrings(string s) {
          int ans = 0;
          int n = s.length();
          for (int l = 0, r = 0, mask = 0; r < n; ++r) {
              int x = s[r] - 'a';
              while ((mask >> x & 1) == 1) {
                  int y = s[l++] - 'a';
                  mask ^= 1 << y;
              }
              mask |= 1 << x;
              ans += r - l + 1 >= 3 ? 1 : 0;
          }
          return ans;
      }
  };
  
  

• func countGoodSubstrings(s string) (ans int) {
  	mask, l := 0, 0
  	for r, c := range s {
  		x := int(c - 'a')
  		for (mask>>x)&1 == 1 {
  			y := int(s[l] - 'a')
  			l++
  			mask ^= 1 << y
  		}
  		mask |= 1 << x
  		if r-l+1 >= 3 {
  			ans++
  		}
  	}
  	return
  }
  
  

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