Java Program to Calculate nCr

In the previous article, we have seen Java Program to Calculate Future Investment Value

In this article we will see how to calculate nCr using Java programming language.

Java Program to Calculate nCr

Before jumping into the program let’s know about nCr.

nCr:

nCr is the probability function which represents combinations.

nCr is the selection of objects from group of objects without caring about order of objects means in case of nCr order of objects does not matter.

nCr = n!/[r! (n-r)!]

Where, selecting r objects from n number of objects.

Let’s see different ways to find future investment value.

By Using Static Input Value
By Using User Input Value

Method-1: Java Program to Calculate nCr By Using Static Input Value

Approach:

Declare the value of n and r value.
Check if n value is greater than r value or not if yes then call findCombination() method.
Else nCr value can not be found out as n value is less than r.
Declare a method factorial() to find factorial of a number.
Inside findCombination() method using the formula find nCr value.

Program:

import java.util.*;

class Main
{
    public static void main(String arg[])	
    {
        //Scanner class object created
        Scanner sc=new Scanner(System.in);
        //n value declared
        int n=20;
        //r value declared
        int r=10;
        //checking n is greater than equal to r or not
        if(n>=r)
        {
    		System.out.println("Value of "+n+"c"+r+" : "+ findCombination(n,r));
        }
        else
        {
        	System.out.println("r value can not be more than n value");
        }
        
    }	
    
    //factorial() method to find factorial of a number
    public static double factorial(double n)
    {
        int i=1;
        double fact=1;
        while(i<=n)
        {
       	   fact=fact*i;
           i++;
 	    }
  	      return fact;
    }

    //findCombination() method to find combinations i.e. nCr value
     public static double findCombination(int n, int r)
    {
        //finding nCr value
        double nCr=factorial(n)/(factorial(r)*(factorial(n-r)));
        //returning nCr value
        return nCr;
    }
}

Output:

Value of 20c10 : 184756.0

Method-2: Java Program to Calculate nCr By Using User Input Value

Approach:

Take input of n and r value.
Check if n value is greater than r value or not if yes then call findCombination() method.
Else nCr value can not be found out as n value is less than r.
Declare a method factorial() to find factorial of a number.
Inside findCombination() method using the formula find nCr value.

Program:

import java.util.*;

class Main
{
    public static void main(String arg[])	
    {
        //Scanner class object created
        Scanner sc=new Scanner(System.in);
        //taking input of n value
        System.out.println("Enter n value: ");
        int n=sc.nextInt();
        //taking input of r value
        System.out.println("Enter r value: ");
        int r=sc.nextInt();
        //checking n is greater than equal to r or not
        if(n>=r)
        {
    		System.out.println("Value of "+n+"c"+r+" : "+ findCombination(n,r));
        }
        else
        {
        	System.out.println("r value can not be more than n value");
        }
        
    }	
    
    //factorial() method to find factorial of a number
    public static double factorial(double n)
    {
        int i=1;
        double fact=1;
        while(i<=n)
        {
       	   fact=fact*i;
           i++;
 	    }
  	      return fact;
    }

    //findCombination() method to find combinations i.e. nCr value
     public static double findCombination(int n, int r)
    {
        //finding nCr value
        double nCr=factorial(n)/(factorial(r)*(factorial(n-r)));
        //returning nCr value
        return nCr;
    }
}

Output:

Enter n value: 
10
Enter r value: 
5
Value of 10c5 : 252.0

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