USACO 3.4 Electric Fence(pick定理)

模板题。精度让我错了一次。

 1 /*

 2       ID: cuizhe

 3       LANG: C++

 4       TASK: fence9

 5 */

 6 #include <cstdio>

 7 #include <cstring>

 8 #include <iostream>

 9 #include <cmath>

10 using namespace std;

11 int gcd(int a,int b)

12 {

13     return b == 0?a:gcd(b,a%b);

14 }

15 int main()

16 {

17     int x,y,p;

18     int a,s,b;

19     freopen("fence9.in","r",stdin);

20     freopen("fence9.out","w",stdout);

21     scanf("%d%d%d",&x,&y,&p);

22     s = p*y;

23     b = gcd(x,y)+p;

24     b += gcd(fabs(p-x),y);

25     a = (s+2-b)/2;

26     printf("%d\n",a);

27     return 0;

28 }