pow() seems to be out by one here

Question

What\'s going on here:

#include 
#include 
int main(void) {
    printf(\"17^12 = %lf\\n\", pow(17, 12));
    printf(\"17^13 = %l         


        

Answer 1

If your input arguments are non-negative integers, then you can implement your own pow.

Recursively:

unsigned long long pow(unsigned long long x,unsigned int y)
{
    if (y == 0)
        return 1;
    if (y == 1)
        return x;
    return pow(x,y/2)*pow(x,y-y/2);
}

Iteratively:

unsigned long long pow(unsigned long long x,unsigned int y)
{
    unsigned long long res = 1;
    while (y--)
        res *= x;
    return res;
}

Efficiently:

unsigned long long pow(unsigned long long x,unsigned int y)
{
    unsigned long long res = 1;
    while (y > 0)
    {
        if (y & 1)
            res *= x;
        y >>= 1;
        x *= x;
    }
    return res;
}