Permutation and Combination c++ logical error - c++11

Question

This is my assignment, i finished writing my code and it does compile but it is not giving the right answer. So i know there is some logical error but i cannot find out what.
Plz check and tell me, simple code to calculate permutations and combinations
#include <iostream>
using namespace std;
int factorial(int n)
{
if (n == 0 or n == 1)
{
return 1;
}
else
{
return n * factorial(n - 1);
}
}
int permutation(int a, int b)
{
//factorial(a);
int perm = factorial(a) / factorial(a - b);
return perm;
}
int combination(int a, int b)
{
int permutation(int a, int b);
int factorial(int n);
return permutation(a, b) / factorial(b);;
}
int main()
{
int n;
int r;
cout << "Enter n: " << endl;
cin >> n;
cout << "Enter r: " << endl;
cin >> r;
int factorial(int n);
int permutation(int n, int r);
int combination(int n, int r);
if (n >= r)
{
cout << "Permutuation: " << permutation << endl;
cout << "Combination: " << combination << endl;
}
else
{
cout << "Invalid" << endl;
}
return 0;
}
The answer given by the console
Enter n:
6
Enter r:
5
Permutuation: 00AC1375
Combination: 00AC133E

Answer 1

There are a number of errors in your code. First, you should not re-declare your 'permutation' and 'combination' functions inside other functions.
EDIT: Actually, this is not an error but, in my opinion, very bad practice. You could accidentally 'hide' the actual function declaration, which is already provided as you have defined both before any of the calling functions.
Second, your cout << permutation << endl; code is printing a function! This will be taken as meaning the address of that function, which is what you are seeing (HEX addresses).
Here's a 'fixed' version that works (with comments).
#include <iostream>
#include <iso646.h> // Need this in order to use "or" in place of "||"
using namespace std;
int factorial(int n)
{
if (n == 0 or n == 1) {
return 1;
}
else {
return n * factorial(n - 1);
}
}
int permutation(int a, int b)
{
//factorial(a);
int perm = factorial(a) / factorial(a - b);
return perm;
}
int combination(int a, int b)
{
// int permutation(int a, int b); // You don't need to redeclare function inside another one ...
// int factorial(int n);
return permutation(a, b) / factorial(b);;
}
int main()
{
int n, r;
cout << "Enter n: " << endl;
cin >> n;
cout << "Enter r: " << endl;
cin >> r;
// int factorial(int n);
int p = permutation(n, r); // This is how to call your functions ...
int c = combination(n, r); // and assign their returns to values.
if (n >= r) {
cout << "Permutuation: " << p << endl; // Output the values ...
cout << "Combination: " << c << endl; // ...from the functions
}
else {
cout << "Invalid" << endl;
}
return 0;
}
Feel free to ask for further explanations if there's anything I've done that you don't understand.