1534. Count Good Triplets-统计好三元组

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

Solution in python:

class Solution:
    def countGoodTriplets(self, arr: List[int], a: int, b: int, c: int) -> int:
        count = 0
        for i in range(len(arr)):
            for j in range(i+1, len(arr)):
                for k in range(j+1, len(arr)):
                    if (abs(arr[i]-arr[j]) <= a) and (abs(arr[j]-arr[k]) <= b) and (abs(arr[i]-arr[k]) <= c):
                        count += 1
        return count