[LeetCode]#1534. Count Good Triplets

Environment: Python 3.8

Key technique: for

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)].

Analysis:

1. Match three conditions as below.
2. If get 3 passes, return 1 match.

Solution:

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

Submissions:

Reference:

https://leetcode.com/problems/count-good-triplets/discuss/980046/Python3%3A-Not-efficient(at-all)-nested-for-loops-solution