poj 2029 二维树状数组

思路：简单树状数组

#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<cstdio>

#include<vector>

#include<string>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define pb push_back

#define mp make_pair

#define Maxn 120

#define Maxm 80002

#define LL __int64

#define Abs(x) ((x)>0?(x):(-x))

#define lson(x) (x<<1)

#define rson(x) (x<<1|1)

#define inf 0x7fffffff

#define lowbit(x) (x&(-x))

#define Mod 1000000007

using namespace std;

int c[Maxn][Maxn],w,h,n;

void update(int x,int y)

{

    int yy=y;

    while(x<=w){

        y=yy;

        while(y<=h){

            c[x][y]++;

            y+=lowbit(y);

        }

        x+=lowbit(x);

    }

}

int sum(int x,int y)

{

    int sum=0,yy=y;

    while(x){

        y=yy;

        while(y){

            sum+=c[x][y];

            y-=lowbit(y);

        }

        x-=lowbit(x);

    }

    return sum;

}

int main()

{

    int n,i,j,x,y;

    while(scanf("%d",&n)!=EOF,n){

        memset(c,0,sizeof(c));

        scanf("%d%d",&w,&h);

        for(i=1;i<=n;i++){

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

            update(x,y);

        }

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

        int ans=0;

        for(i=x;i<=w;i++){

            for(j=y;j<=h;j++){

                ans=max(ans,sum(i,j)-sum(i-x,j)-sum(i,j-y)+sum(i-x,j-y));

            }

        }

        printf("%d\n",ans);

    }

    return 0;

}