POJ 2398 Toy Storage（叉积）

Toy Storage

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 3858		Accepted: 2273

Description

Mom and dad have a problem: their child, Reza, never puts his toys away when he is finished playing with them. They gave Reza a rectangular box to put his toys in. Unfortunately, Reza is rebellious and obeys his parents by simply throwing his toys into the box. All the toys get mixed up, and it is impossible for Reza to find his favorite toys anymore. 
Reza's parents came up with the following idea. They put cardboard partitions into the box. Even if Reza keeps throwing his toys into the box, at least toys that get thrown into different partitions stay separate. The box looks like this from the top: 

We want for each positive integer t, such that there exists a partition with t toys, determine how many partitions have t, toys.

Input

The input consists of a number of cases. The first line consists of six integers n, m, x1, y1, x2, y2. The number of cardboards to form the partitions is n (0 < n <= 1000) and the number of toys is given in m (0 < m <= 1000). The coordinates of the upper-left corner and the lower-right corner of the box are (x1, y1) and (x2, y2), respectively. The following n lines each consists of two integers Ui Li, indicating that the ends of the ith cardboard is at the coordinates (Ui, y1) and (Li, y2). You may assume that the cardboards do not intersect with each other. The next m lines each consists of two integers Xi Yi specifying where the ith toy has landed in the box. You may assume that no toy will land on a cardboard. 

A line consisting of a single 0 terminates the input.

Output

For each box, first provide a header stating "Box" on a line of its own. After that, there will be one line of output per count (t > 0) of toys in a partition. The value t will be followed by a colon and a space, followed the number of partitions containing t toys. Output will be sorted in ascending order of t for each box.

Sample Input

4 10 0 10 100 0
20 20
80 80
60 60
40 40
5 10
15 10
95 10
25 10
65 10
75 10
35 10
45 10
55 10
85 10
5 6 0 10 60 0
4 3
15 30
3 1
6 8
10 10
2 1
2 8
1 5
5 5
40 10
7 9
0

Sample Output

Box
2: 5
Box
1: 4
2: 1
题意：爸爸妈妈嫌孩子乱丢玩具，于是就给孩子整了一个箱子；里面有很多挡板
孩子就很听话的把玩具“扔”进去，聪明的小伙伴去帮助他，然让他知道他把玩具扔哪了？
输入 
     第一行 六个数 n,m,x1,y1,x2,y2; x1和y1是箱子的左上角，x2,y2是箱子的右下角
     接下来的n行是挡板的两个参数，xx1,xx2  挡板的坐标为（xx1,y1,xx2,y2);
输出  
     有几个箱子里面装着几个玩具
代码
#include<stdio.h>
#include<iostream>
#include<algorithm>
#include<string.h>
#define MAXN 1000
using namespace std;
struct st
{
    int x,y;
} toy[MAXN+10];
struct stu
{
    int x1,x2;
} board[MAXN+10];
int cmp(struct stu a,struct stu b)
{
    if(a.x1==b.x1)
        return a.x2<b.x2;
    return a.x1<b.x1;
}
int cross(int a1,int a2,int b1,int b2,int c1,int c2)
{
    return (b1-a1)*(c2-a2)-(b2-a2)*(c1-a1);
}
int main()
{
    int n,m;
    int x1,x2,y1,y2,i,j,ans[MAXN+10],ans1[MAXN+10];
    while(cin >> n&&n)
    {
        cin >> m >> x1 >> y1 >> x2 >> y2;
        memset(ans,0,sizeof(ans));
        memset(ans1,0,sizeof(ans1));
        for(i=1; i<=n; i++)
            cin >> board[i].x1 >> board[i].x2;
        board[n+1].x1 = x2;
        board[n+1].x2 = x2;
        sort(board,board+n+2,cmp);
        for(i=0; i<m; i++)
            cin >>toy[i].x >> toy[i].y;
        for(i=0; i<m; i++)
            for(j=0; j<=n; j++)
            {
                if(cross(board[j].x1,y1,board[j].x2,y2,toy[i].x,toy[i].y)>0 && cross(board[j+1].x1, y1,board[j+1].x2,y2,toy[i].x,toy[i].y)<0)
                {
                    ans[j+1]++;
                }
            }
        cout << "Box" << endl;
        for(j=0; j<=n+1; j++)
            if(ans[j]!=0)
                ans1[ans[j]]++;
        for(j=0;j<=n;j++)
            if(ans1[j])
            cout << j <<": " <<ans1[j] << endl;
    }
    return 0;
}