Question

I’m trying to solve Project Euler #9, which is http://projecteuler.net/index.php?section=problems&id=9.

I’ve looked through this code, and the logic seems right…but I’m not getting any output at all, not even the printfs in the loop. I’m (obviously) a C newbie, trying to learn from higher level languages…could you tell me what’s going wrong?

#include <stdio.h>

int main(){
    unsigned int a=0, b=0, c=0;
    short int pass=0;
    while(!pass){
        //printf("a = %4d\n", a);
        a++;
        b=a;
        while(!pass){
            b++;
            c=1000-a-b;
            if(b>=c) break;
            if(a*a+b*b==c*c) pass = 1;
        }
    }
    printf("a=%d, b=%d, c=%d, a*b*c=%d, a+b+c=%d\n", a, b, c, a*b*c,a+b+c);
    return 1;
}

Thanks so much.

EDIT: Okay, I’ve fixed the floating point problem as shown above, but now a never goes above two for some reason, making it loop infinitely.

EDIT: I fixed some bugs, but still, it returns a=33, b=483, c=484, a*b*c=7714476, a+b+c=1000, which isn’t quite right. 🙁

Wow, I was overcomplicating it. It works now. Thanks everyone.

Answer 1

if(floor(sc) != sc) continue; // we only want integer values of c

It’s possible that that floor(sc) is always inequel to sc. Because sc is a double, operations on it will introduce small errors. Try defining a small variable to signify “close enough” and check if it is within that range. See here for strategies around this.

Not sure if there are other issues with your code.