POJ2029--Get Many Persimmon Trees(枚举+二维树状数组)

暴力枚举起点，然后就是裸的二维树状数组。

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <math.h>
#include <queue>
#include <stack>
#include <vector>
#include <ctype.h>
#define INF 999999999
#define M 105
#define LL long long
#define Min(a,b) a<b?a:b
#define Max(a,b) a>b?a:b
using namespace std;

int c[M][M];
int n,m;

int Lowbit(int x)
{
return x&(-x);
}

void Update(int x,int y,int d)
{
int i,j;
for(i=x;i<=n;i+=Lowbit(i))
{
for(j=y;j<=m;j+=Lowbit(j))
c[i][j]+=d;
}
}

int Getsum(int x,int y)
{
int sum=0;
int i,j;
for(i=x;i>0;i-=Lowbit(i))
{
for(j=y;j>0;j-=Lowbit(j))
{
sum+=c[i][j];
}
}
return sum;
}

int main()
{
int k,x,y,i,j;
while(scanf("%d",&k),k)
{
scanf("%d%d",&n,&m);
memset(c,0,sizeof(c));
while(k--)
{
int a,b;
scanf("%d%d",&a,&b);
Update(a,b,1);
}
scanf("%d%d",&x,&y);
int max=-INF;
int ans=0;
for(i=x;i<=n;i++)
{
for(j=y;j<=m;j++)
{
ans=Getsum(i,j)-Getsum(i,j-y)-Getsum(i-x,j)+Getsum(i-x,j-y);
if(ans>max)
max=ans;
}
}
printf("%d\n",max);
}
return 0;
}