C ++Program Uses Factorial to Calculate Combinations

The following is an example of calculating combinations using factorial.

Example

#include <iostream>
using namespace std;
int fact(int n) {
　　　if (n == 0 || n ==　1)
　　　return　1;
　　　else
　　　return n　*　fact(n　-　1);
}
int main() {
　　　int n, r, result;
　　　cout << "Enter n : ";
　　　cin >> n;
　　　cout << "\nEnter r : ";
　　　cin >> r;
　　　result = fact(n　/　(fact(r　*　fact(n-r));
　　　cout << "\nThe result: " << result;
　　　return 0;
}

Output result

Enter n:　10
Enter r:　4
The result:　210

In the above program, the code exists infact()The function calculates the factorial of a number.

if (n == 0 || n ==　1)
return　1;
else
return n　*　fact(n　-　1);

In thismain()In the method, the combination of two numbers entered by the user is calculated. The variable "result" stores the calculated value of the combination using factorial.

cout << "Enter n : ";
cin >> n;
cout << "\nEnter r : ";
cin >> r;
result = fact(n　/　(fact(r　*　fact(n-r));