an amusing bug

math-test.c (text/plain), 1.25 KB, created by Rafał Mużyło on 2009-07-02 17:35:51 UTC

#include <stdio.h>

static int gcd(int a, int b) {
        int r;
        if (a < 0)
                a = -a;
        if (b < 0)
                b = -b;
        while (b != 0) {
                r = a%b;
                a = b;
                b = r;
        }
        return a;
}

int main(void) {
        int tc, cs;
        int x0, y0, x1, y1, dx, dy;
        int n, i;
        int l;
        int area;

        scanf("%d", &tc);
        for (cs = 0; cs != tc; ++cs) {
                scanf("%d", &n);

                x0 = 0; y0 = 0;
                x1 = 0; y1 = 0;
                l = 0;
                area = 0;
                for (i = 0; i != n; ++i) {
                        scanf("%d%d", &dx, &dy);
                        l+= gcd(dx, dy);
                        x1 = x0 + dx;
                        y1 = y0 + dy;
                        //printf("%d\n", x0*y1-x1*y0 );
                        area += x0*y1-x1*y0;
                        //area += (x0*(y0+dy) - (x0+dx)*y0);
                        x0 = x1; y0 = y1;
                }
                if (area < 0)
                        area = -area;

                printf("Scenario #%d:\n", cs+1);
                printf("%d %d %d.%d\n\n", (area+2-l)/2, l, area/2, area&1 ? 5 :
0);
        }

        return 0;
}