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Java Program to Perform nCr (rcombinations)
In this article, we will understand how to compute the combination using n and r values. The nCr is calculated using the formula −
(factorial of n) / (factorial of (n-r))
Below is a demonstration of the same −
Input
Suppose our input is −
Value of n : 6 Value of r : 4
Output
The desired output would be −
The nCr value is : 15
Algorithm
Step 1 - START Step 2 - Declare two integer values namely n and r. Step 3 - Read the required values from the user/ define the values Step 4 - Define two functions, one function to calculate the factorial of n and (n-r) and other to compute the formula : (factorial of n) / (factorial of (n-r)) and store the result. Step 5 - Display the result Step 6 - Stop
Example 1
Here, the input is being entered by the user based on a prompt. You can try this example live in ourcoding ground tool 
.
import java.util.*;
public class Combination {
static int Compute_nCr(int n, int r){
return my_factorial(n) / (my_factorial(r) *
my_factorial(n - r));
}
static int my_factorial(int n){
int i, my_result;
my_result = 1;
for (i = 2; i <= n; i++)
my_result = my_result * i;
return my_result;
}
public static void main(String[] args){
int n,r;
System.out.println("Required packages have been imported");
Scanner my_scanner = new Scanner(System.in);
System.out.println("A reader object has been defined ");
System.out.print("Enter the value of n : ");
n = my_scanner.nextInt();
System.out.print("Enter the value of r : ");
r = my_scanner.nextInt();
System.out.println("The combination value for the given input is = "+Compute_nCr(n, r));
}
}Output
Required packages have been imported A reader object has been defined Enter the value of n : 6 Enter the value of r : 4 The combination value for the given input is = 15
Example 2
Here, the integer has been previously defined, and its value is accessed and displayed on the console.
public class Combination {
static int Compute_nCr(int n, int r){
return my_factorial(n) / (my_factorial(r) *
my_factorial(n - r));
}
static int my_factorial(int n){
int i, my_result;
my_result = 1;
for (i = 2; i <= n; i++)
my_result = my_result * i;
return my_result;
}
public static void main(String[] args){
int n,r;
n = 6 ;
r = 4 ;
System.out.println("The n and r values are defined as " +n + " and " +r);
System.out.println("The combination value for the given input is = "+Compute_nCr(n, r));
}
}Output
The n and r values are defined as 6 and 4 The combination value for the given input is = 15
Updated on: 22-Feb-2022
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