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TO GENERATE nCr AND nPr IN C

Code

#include<stdio.h>
int fact(int num)
{
int f=1;
int i;
for(i=1;i<=num;i++)
{
  f=f*i;	
}
return f;
}
int main()
{
int n,r;
int ncr,npr;
printf("nCr & nPr CALCULATOR :\n");
printf("ENTER THE VALUES OF n & r :\n");
scanf("%d %d",&n;,&r;);
ncr=fact(n)/(fact(r)*fact(n-r));
npr=fact(n)/(fact(n-r));
printf("%dC%d : %d\n",n,r,ncr);
printf("%dP%d : %d",n,r,npr);
return 0;
}

Output

nCr & nPr CALCULATOR :
ENTER THE VALUES OF n & r :10 8
10C8 : 45
10P8 : 1814400

What we did - Our Approach

In this problem we have to generate the measure of ⁿC_r and ⁿP_r for given values of 'n' and 'r'. We have following formulaes to calculate ⁿC_r and ⁿP_r respectively :

ⁿC_r = n! / r!*(n-r)!

ⁿP_r = n! /(n-r)!

Now after breaking this formula,we see that,all we have to do is find the factorial of each parameter i.e n,r,n-r. So,after finding the factorial,we put the values in formula.