Thread: Problem with multiplication

Why don't I get the same result if I multiply all together in the first example?
The second gives the good result.

Code:

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


int formatThousands(long long value)
{
    string num = to_string(value);
    int insertPosition = num.length() - 3;
    while (insertPosition > 0)
    {
        num.insert(insertPosition, " ");
        insertPosition-=3;
    }
    cout << num << endl;
    return 0;
}


int main()
{
    // 1.
    long long int chance = 0;
    chance += 49*48*47*46*45*44;
    cout << " Chance: ";
    formatThousands(chance);
    cout << "\n\n";

    //2.
    chance=0;
    chance += (49*48*47*46*45);
    chance *= 44;
    cout << " Chance: ";
    formatThousands(chance);
    cout << "\n\n";


    return 0;
}

Need to declare the constants as long long, as the product is > 32 bits.

Code:

    chance += 49ll*48ll*47ll*46ll*45ll*44ll;

or just casting any of them should promote all to long long:

Code:

    chance += (long long)49*48*47*46*45*44;

Ah, OK, thanks for the explanation!

Originally Posted by rcgldr

or just casting any of them should promote all to long long:

Or you can specify that one of the constants is a long long, e.g. 49ll*48*47*46*45*44.