Count the number of possible triangles.cpp

//{ Driver Code Starts
#include <bits/stdc++.h>
using namespace std;


// } Driver Code Ends
class Solution {
  public:
    // Function to count the number of possible triangles.
    int countTriangles(vector<int>& arr) {
        // code here
        int n = arr.size();
        sort(arr.begin(), arr.end());
        int count = 0;    
        
        for (int i = n - 1; i >= 2; i--) {
            int left = 0;
            int right = i - 1;
            while (left < right) {
                if (arr[left] + arr[right] > arr[i]) {
                    count += (right - left);
                    right--;
                } 
                else {
                    left++;
                }
            }
        }
        return count;

    }
};


//{ Driver Code Starts.

int main() {
    int t;
    cin >> t;
    cin.ignore(); // To ignore the newline after the integer input
    while (t--) {
        int n;
        vector<int> a;
        string input;

        // Input format: first number n followed by the array elements
        getline(cin, input);
        stringstream ss(input);
        int num;
        while (ss >> num)
            a.push_back(num);

        Solution obj;
        cout << obj.countTriangles(a) << "\n~\n";
    }

    return 0;
}

// } Driver Code Ends