poj 2029 Get Many Persimmon Trees

http://poj.org/problem?id=2029

#include <cstdio>
#include <cstring>
#include <algorithm>
#define maxn 200
using namespace std;

int dp[maxn][maxn];
int n,s,t,w,h;
int a[maxn][maxn];

int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        if(n==0) break;
        scanf("%d%d",&w,&h);
        memset(dp,0,sizeof(dp));
        memset(a,0,sizeof(a));
        for(int i=1; i<=n; i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            a[x][y]=1;
        }
        scanf("%d%d",&s,&t);
        for(int i=1; i<=w; i++)
        {
            for(int j=1; j<=h; j++)
            {
                dp[i][j]=dp[i-1][j]+dp[i][j-1]-dp[i-1][j-1]+a[i][j];
            }
        }
        int ans=-1;
        for(int i=1; i<=w; i++)
        {
            for(int j=1; j<=h; j++)
            {
                int x1=i-s+1;
                int y1=j-t+1;
                if(x1<1||y1<1) continue;
                ans=max(ans,dp[i][j]-dp[x1-1][j]-dp[i][y1-1]+dp[x1-1][y1-1]);
            }
        }
        printf("%d
",ans);
    }
    return 0;
}