Question

write a program which inputs an integer value , checks that it is positive, and outputs its factorial, using the formulas:
factorial(0) = 1
factorial(n) = n * factorial(n-1)

Answer 1

#include <iostream>

int factorial(int n){
int res=1;
for(int i = 1; i <= n; i++)
& res = res*i;
return res;
}

bool positive(int n){
if (n>=0) { std::cout<<"positive\n"; return true; }
else { std::cout<<"negative\n"; return false; }
}

void main(){
int m;
std::cout<<"Enter an integer: ";
std::cin>>m;
if (positive(m)) std::cout<<factorial(m)<<"\n";
system("pause");
}