What's wrong with factorial function code in this Pascal triangle?

Question

can anyone explain why first fact() function code doesn't give me correct output but second one does? what's wrong with the commented factorial function code???

#include <iostream>
using namespace std;
// int fact(int n){
//     for (int i = n-1; i > 0; i--){
//         n = n * i;
//     }
//     return n;
// }

int fact(int n){
    int temp=1;
    for (int i = 2; i <=n; i++){
        temp= temp * i;
    }
    return temp;
}

int nCr(int n, int r){
    int temp=(fact(n) / (fact(n - r) * fact(r)));
    return temp;
}
int main(){
    int n;
    cout << "enter no: ";
    cin >> n;
    for (int i = 0; i < n;i++){
        for (int k = 1; k < (n - i);k++)
            cout << " ";
        for (int j = 0; j <= i; j++)
        {
            cout << nCr(i, j) << " ";
        }
        cout << endl;
    }
    return 0;
}

*what's wrong with the commented factorial function code???* -- [What is a debugger and how will it help me diagnose issues?](https://stackoverflow.com/questions/25385173/what-is-a-debugger-and-how-can-it-help-me-diagnose-problems) and [How to debug small programs](https://ericlippert.com/2014/03/05/how-to-debug-small-programs/) — PaulMcKenzie, Jun 16 '21 at 14:30

score 0 · Answer 1 · answered Jun 16 '21 at 14:26

The second fact function correctly returns 1 when n = 0, but the first one wrongly returns 0 when n = 0.

Adding check for this case will make the first function work well.

int fact(int n){
    if (n == 0) return 1; // check for n = 0 case
    for (int i = n-1; i > 0; i--){
        n = n * i;
    }
    return n;
}

What's wrong with factorial function code in this Pascal triangle?

1 Answers1