USACO3.43Electric Fence(pick定理）

忘记pick定理是什么了 想枚举来着 。。没枚出来

有篇pick定理的证明 貌似挺好 也没太看懂

 1 /*

 2     ID: shangca2

 3     LANG: C++

 4     TASK: fence9

 5  */

 6 #include <iostream>

 7 #include<cstdio>

 8 #include<cstring>

 9 #include<algorithm>

10 #include<stdlib.h>

11 using namespace std;

12 int gcd(int x,int y)

13 {

14     return y==0?x:gcd(y,x%y);

15 }

16 int main()

17 {

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

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

20     int n,m,p,k=0,ans;

21     double s;

22     cin>>n>>m>>p;

23     s = p*m/2.0;

24     k+=p;

25     k+=gcd(n,m);

26     k+=abs(gcd(n-p,m));

27     ans = (s+1)-k/2;

28     cout<<ans<<endl;

29     return 0;

30 }

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