Program 177:To Calculate Permutation value nPr

Program 177:
 

#include<stdio.h>
int factorial(int);
main()
{ 
int n,r;
float nPr;
printf("Enter value of n in nPr\n");
scanf("%d",&n);
printf("Enter value of r in nPr\n");
scanf("%d",&r);
if(n>=r&&n>=0&&r>=0)
{
   nPr=(float)factorial(n)/factorial(n-r);
   printf("Value of %dP%d=%f\n",n,r,nPr);
}
else
{
 printf("Invalid Entry\n");
}

}

int factorial(int num)
{
 int i,fact=1;
 for(i=1;i<=num;i++)
 {
  fact=fact*i;
 }
 
 return(fact);
}

Explanation:
Formula for permutation us nPr=n!/(n-r)! under condition of  n>=r,n>=0,r>=0

int factorial(int); → function Declaration

1. Here we used
   
   • n → To store Value
   • r → To store Value
   • nPr → To store output

2. printf("Enter value of n in nPr\n");
   scanf("%d",&n);
   printf("Enter value of r in nPr\n");
   scanf("%d",&r);

   Takes values of n and r
3.  
   

   if(n>=r&&n>=0&&r>=0)
   {
      nPr=(float)factorial(n)/factorial(n-r);
      printf("Value of %dP%d=%f\n",n,r,nPr);
   }
   else
   {
    printf("Invalid Entry\n");
   }

   Checks the required condition as mentioned in the above formula.If the condition is satisfied then if part is executed otherwise the else part.

4. nPr=(float)factorial(n)/factorial(n-r);
      printf("Value of %dP%d=%f\n",n,r,nPr);

   As per formula we need to get factorial of 'n' and 'n-r'.factorial (n) gets the factorial of n same as factorial(n-r).As the factorial(n) send the value of n to factorial function .

   int factorial(int num)
   {
    int i,fact=1;
    for(i=1;i<=num;i++)
    {
     fact=fact*i;
    }
    
    return(fact);
   }

   After getting the value from factorial it calculates formula and store in nPr.
5. To understand factorial in detail CLICK HERE.

Output: