why my factorial is showing 0

Question

#include <iostream>
#include <cmath>
using namespace std;

void power(int *a,int *b,int *c);
void factorial(int *a ,int *b,int *c);
int main()
{
    int x,y,z1,z2;
    
    cout<<"Enter the value of x :" ;
    cin>>x;
    cout<<"Enter the value of y :";
    cin>>y;
    
    power(&x,&y,&z1);
    
    cout<<z1<<endl;
    factorial(&x,&y,&z2);
     cout<<z2<<endl;
    
    if(z1>z2){
        cout<<x<<"^"<<y<<"is greater than "<<x<<"!"<<"+"<<y<<"!";
    }
    else{
        cout<<x<<"^"<<y<<"is smaller than "<<x<<"!"<<"+"<<y<<"!";
    }
    return 0;
}  
void power(int *a,int *b,int *c){
    
    *c=pow(*a,*b);
    
}

void factorial(int *a ,int *b,int *c){
    
    int *i,*fact1,*fact2 ;
    i=new int;
    fact1 =new int;
    fact2 =new int;
    
    *fact1=1;
    *fact2=1;
    
    if(*a>1){
        for(*i=1;*i<=*a;*i++){
            *fact1 =(*fact1) * (*i);
        }
    }

    if(*b>1){
        for(*i=1;*i<=*b;*i++){
            *fact2 =(*fact2) * (*i);
        }
    }

    
    cout<<*fact1<<endl<<*fact2<<endl;
    
    *c= *fact1 + *fact2;
    
    
}

Answer 1

You are way overusing pointers unnecessarily. This also somewhat slows down your code.

Why your code prints the wrong value is that you got confused on the operator precedence. Post-increment comes before dereferencing pointes, so 

for (*i = 1; *i <= *a; *i++)

doesn't do what you think it does. The above code actually moves the pointer (i) to the next int in the memory, then dereferences it.

What you should have done is

for (*i = 1; *i <= *a; (*i)++)

Nevertheless, your code is way overcomplicated.

Here's my enhancement of your code:

#include <iostream>
#include <cmath>

static long int factorial(int n)
{
    long int product = 1;
    while (n > 1)
        product *= n--;

    return product;
}

int main()
{
    int x, y;
    
    std::cout << "Enter the value of x: ";
    std::cin >> x;
    std::cout << "Enter the value of y: ";
    std::cin >> y;
    
    double power = pow(x, y);
    long int factSum = factorial(x) + factorial(y);

    std::cout << x << "^" << y << " = " << power;
    if (power > factSum)
        std::cout << " is greater than ";
    else if (power < factSum)
        std::cout << " is smaller than ";
    else
        std::cout << " is the same as ";
    std::cout << x << "!" << " + " << y << "! = " << factSum << std::endl;

    return 0;
}

Comments

THANK YOU :)

Answer 2

#include <iostream>
using namespace std;

int main()
{
    int num,fac= 1,i;

    cout << "Enter a number";
    cin >> num;
        for(i = 1; i <=num; i++)
        {
            fac =fac* i;
        }
        cout << "Factorial of " <<fac;    

    return 0;
}