How do I compute N factorial in C++?

[carl123]

Write a program that let's a user enter N and that outputs N! (meaning N*(N-1)*(N-2)*...*2*1). Hint: Initialize a variable totalValue to N, and use a loop variable i that counts from N-1 down to 1.

#include <iostream>
using namespace std;

int main() {
int totalVal = 0;
int userInt = 0;

// FIXME: Ask user to input an integer, store in userInt

totalVal = userInt;
// FIXME: Add while loop that counts down to 1, updating totalVal

count << userInt <<"! is " << totalVal << endl;

return 0;
}

 

[Conn_coord]

#include <iostream>
using namespace std;

// If no checks for invalid input

int main() {
int totalVal = 0;
int userInt = 0;

// FIXME: Ask user to input an integer, store in userInt
count << ("Enter integer value > 0") <<endl;
cin >> userInt;

totalVal = userInt;
// FIXME: Add while loop that counts down to 1, updating totalVal

int temp = userInt;
while(temp>1)
{
totalVal*= --temp;
}

count << userInt <<"! is " << totalVal << endl;

return 0;
}

 

[Halc]

The while loop can be
while(temp > 2);
No point in multiplying by 1.

The program only works up to 12! Probably should be a bounds check for an integer from 1 to 12.
It gets a lot more complicated if you want it to go beyond 20!

 

[Conn_coord]

I just completed the program. Did not write new :)