LeetCode1534. Count Good Triplets

一、题目

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

二、题解

class Solution {
public:
    int countGoodTriplets(vector<int>& arr, int a, int b, int c) {
        int res = 0;
        int n = arr.size();
        for(int i = 0;i < n;i++){
            for(int j = i + 1;j < n;j++){
                bool fa = false;
                if(abs(arr[i] - arr[j]) <= a) fa = true;
                for(int k = j + 1;k < n;k++){
                    bool fb = false,fc = false;
                    if(abs(arr[j] - arr[k]) <= b) fb = true;
                    if(abs(arr[i] - arr[k]) <= c) fc = true;
                    if(fa && fb && fc) res++;
                }
            }
        }
        return res;
    }
};