1534. Count Good Triplets

Description

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

 

Solutions

Solution: Brute Force

• Time complexity: O(n³)
• Space complexity: O(1)

 

JavaScript

/**
 * @param {number[]} arr
 * @param {number} a
 * @param {number} b
 * @param {number} c
 * @return {number}
 */
const countGoodTriplets = function (arr, a, b, c) {
  const n = arr.length;
  let result = 0;

  for (let i = 0; i < n - 2; i++) {
    for (let j = i + 1; j < n - 1; j++) {
      if (Math.abs(arr[i] - arr[j]) > a) continue;

      for (let k = j + 1; k < n; k++) {
        if (Math.abs(arr[j] - arr[k]) > b) continue;
        if (Math.abs(arr[i] - arr[k]) > c) continue;

        result += 1;
      }
    }
  }

  return result;
};