Hello!!! Some one can tell me what's going wrong for this code?I try to calculate the factorial of a number

Question

#include <iostream>
using namespace std;

int main()
{
long long int num,f,i;
i=1;
cin>> num;
while (num<0){cout<<"please another number"<<endl;
cin>>num;}
if(num==0){cout<<"1"<<endl;}
else (num>0){while(i<num){f=num(num-i);i++;}}

return 0;
}

Answer 1

#include <iostream>
using namespace std;

int main()
{
long long int n,i,f;
i=1;
f=1;
cout <<"pleas enter a number"<<endl;
cin >>n;
if(n<0){cout <<"pleas enter a positiv number"<<endl;}
cin >>n;
if(n>=0){if(n>0){while(i<=n){f*=i;i++;}cout <<"result is:"<<endl;cout <<f;}}
else{cout <<"result is:"<<endl;cout <<1;}
return 0;}

Answer 2

Yes is true the f value is reset every time the loop run!!! thanks!!!!

Answer 3

The algorithm seems wrong, even if the syntax was right. (I'm not an expert with C++ but num(num-i) looks wrong)

Trying to calculate f = num*(num-i) will reset f's value every time in the loop. You need to protect the result, not reset it.

Also you need to keep your loop until i greater than the num. Initialize f = 1, then multiply it with i each time.

Like;

f = 1, i = 1;

while(i<=num){
f *= i;
i++;
}

Or like;

while(num){
i *= num--;
}

Answer 4

You're welcome! :)

Answer 5

hello!!! I had modified the code and now it seems it's good.

Answer 6

Yes Renato, well done!

Answer 7

I see you found your answer but I see your code and you can make your code more beautiful by using do while .