# Permutation Program In C

Permutation refers number of ways in which set members can be arranged or ordered in some fashion. The formula of permutation of arranging k elements out of n elements is −

nPk = n! / (n - k)!

## Algorithm

This algorithm only focuses on permutation without going into details of factorial −

```START
Step 1 → Define values for n and r
Step 2 → Calculate factorial of n and (n-r)
Step 3 → Divide factorial(n) by factorial(n-r)
Step 4 → Display result as permutation
STOP
```

## Pseudocode

This algorithm can simply be derived into the below given pseudocode −

```procedure permutation()

Define n and r
P = factorial(n) / factorial(n-r)
DISPLAY P

end procedure
```

## Implementation

Implementation of this algorithm is given below −

```#include <stdio.h>

int factorial(int n) {
int f;

for(f = 1; n > 1; n--)
f *= n;

return f;
}

int npr(int n,int r) {
return factorial(n)/factorial(n-r);
}

int main() {
int n, r;

n = 4;
r = 3;

printf("%dp%d = %d \n", n, r, npr(n,r));

return 0;
}
```

## Output

Output of the program should be −

```4p3 = 24
```
mathematical_programs_in_c.htm
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