poj 1054 The Troublesome Frog

http://poj.org/problem?id=1054

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #define maxn 5001

 5 using namespace std;

 6 

 7 int r,c,n,x2,y2;

 8 bool vis[maxn][maxn];

 9 struct node

10 {

11     int x,y;

12     bool operator <(const node &a)const

13     {

14         return (x<a.x)||(x==a.x&&y<a.y);

15     }

16 }p[maxn*2];

17 

18 int main()

19 {

20     while(scanf("%d%d",&r,&c)!=EOF)

21     {

22         scanf("%d",&n);

23         memset(vis,false,sizeof(vis));

24         for(int i=0; i<n; i++)

25         {

26             scanf("%d%d",&p[i].x,&p[i].y);

27             vis[p[i].x][p[i].y]=true;

28         }

29         sort(p,p+n);

30         int max1=2;

31         for(int i=0; i<n; i++)

32         {

33             for(int j=i+1; j<n; j++)

34             {

35                 int x1=p[j].x-p[i].x;

36                 int y1=p[j].y-p[i].y;

37                 if(p[i].x-x1>=1&&p[i].x-x1<=r&&p[i].y-y1>=1&&p[i].y-y1<=c) continue;

38                 if(!(p[i].x+max1*x1>=1&&p[i].x+max1*x1<=r&&p[i].y+max1*y1>=1&&p[i].y+max1*y1<=c)) continue;

39                 int t1=1;

40                 x2=p[j].x; y2=p[j].y;

41                 while(x2>=1&&x2<=r&&y2>=1&&y2<=c)

42                 {

43                     if(!vis[x2][y2]) break;

44                     if(vis[x2][y2]) {t1++;}

45                     x2=x2+x1;

46                     y2=y2+y1;

47                 }

48                 if(!(x2>=1&&x2<=r&&y2>=1&&y2<=c))

49                 max1=max(max1,t1);

50             }

51         }

52         if(max1<=2) printf("0\n");

53         else

54         printf("%d\n",max1);

55     }

56     return 0;

57 }

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