1534. Count Good Triplets.md

1534. Count Good Triplets

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the first one in Weekly Contest 200.

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Difficulty : Easy

Related Topics : Array

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Given an array of integers arr, and three integers a, b and c. You need to find the number of good triplets.

A triplet (arr[i], arr[j], arr[k]) is good if the following conditions are true:

• 0 <= i < j < k < arr.length
• |arr[i] - arr[j]| <= a
• |arr[j] - arr[k]| <= b
• |arr[i] - arr[k]| <= c

Where |x| denotes the absolute value of x.

Return the number of good triplets.

Example 1:

Input: arr = [3,0,1,1,9,7], a = 7, b = 2, c = 3
Output: 4
Explanation: There are 4 good triplets: [(3,0,1), (3,0,1), (3,1,1), (0,1,1)].

Example 2:

Input: arr = [1,1,2,2,3], a = 0, b = 0, c = 1
Output: 0
Explanation: No triplet satisfies all conditions.

Constraints:

• 3 <= arr.length <= 100
• 0 <= arr[i] <= 1000
• 0 <= a, b, c <= 1000

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Solution

• mine
  • Java
    • BRUTE FORCE Runtime: 10 ms, faster than 100.00%, Memory Usage: 37.6 MB, less than 100.00% of Java online submissions

      // O(N^3)time
      // O(1)space
      public int countGoodTriplets(int[] arr, int a, int b, int c) {
          int n = arr.length;
          int res = 0;
          for(int i = 0; i < n; i++){
              for(int j = i + 1; j < n; j++){
                  if(Math.abs(arr[i] - arr[j]) > a) continue;
                  for(int k = j + 1; k < n; k++){
                      if(Math.abs(arr[j] - arr[k]) <= b
                        && Math.abs(arr[i] - arr[k]) <= c){
                          res++;
                      }
                  }
              }
          }
          return res;
      }
      

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