1534. Count Good Triplets

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

这题想了半天巧解没想出来，直接暴力破解了

class CountGoodTriplets : public Solution {
public:
    void Exec() {

    }
    int countGoodTriplets(vector<int>& arr, int a, int b, int c) {
        int count = 0;
        for (int i = 0; i < arr.size() - 2; i++) {
            for (int j = i + 1; j < arr.size(); j++) {
                if (abs(arr[i] - arr[j]) > a) {
                    continue;
                }
                for (int k = j + 1; k < arr.size() - 1; k++) {
                    if (abs(arr[i] - arr[k]) <= c &&
                    abs(arr[k] - arr[j]) <= b) {
                        ++count;
                    }
                }
            }
        }
        return count;
    }
};