zoj1716简单的二维树状数组

问一个矩形框在一个大矩形内最多能围几个给定的点

都不用排序，先把所有的点加入树状数组，再直接枚举大矩形的每个格子即可

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <string>
#include <stack>
#include <queue>
#include <map>
#include <set>
#include <vector>
#include <math.h>
#include <bitset>
#include <list>
#include <algorithm>
#include <climits>
using namespace std;

#define lson 2*i
#define rson 2*i+1
#define LS l,mid,lson
#define RS mid+1,r,rson
#define UP(i,x,y) for(i=x;i<=y;i++)
#define DOWN(i,x,y) for(i=x;i>=y;i--)
#define MEM(a,x) memset(a,x,sizeof(a))
#define W(a) while(a)
#define gcd(a,b) __gcd(a,b)
#define LL long long
#define N 1005
#define INF 0x3f3f3f3f
#define EXP 1e-8
#define lowbit(x) (x&-x)
const int mod = 1e9+;

int c[N][N],n,m,cnt,s,t;

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

void add(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 main()
{
    int i,j,x,y,ans;
    while(~scanf("%d",&cnt),cnt)
    {
        ans = ;
        scanf("%d%d",&n,&m);
        MEM(c,);
        for(i = ;i<=cnt;i++)
        {
            scanf("%d%d",&x,&y);
            add(x,y,);
        }
        scanf("%d%d",&s,&t);
        for(i = ;i<=n;i++)
        {
            for(j = ;j<=m;j++)
            {
                int x1 = i,y1 = j,x2 = x1+s-,y2 = y1+t-;
                if(x2>n || y2>m) continue;
                int s = sum(x2,y2)+sum(x1-,y1-)-sum(x2,y1-)-sum(x1-,y2);
                ans = max(ans,s);
            }
        }
        printf("%d\n",ans);
    }

    return ;
}