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Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 11023    Accepted Submission(s): 4530

Problem Description

There is a pile of n wooden sticks. The length and weight of each stick are known in advance. The sticks are to be processed by a woodworking machine in one by one fashion. It needs some time, called setup time, for the machine to prepare processing a stick. The setup times are associated with cleaning operations and changing tools and shapes in the machine. The setup times of the woodworking machine are given as follows:

(a) The setup time for the first wooden stick is 1 minute.
(b) Right after processing a stick of length l and weight w , the machine will need no setup time for a stick of length l' and weight w' if l<=l' and w<=w'. Otherwise, it will need 1 minute for setup.

You are to find the minimum setup time to process a given pile of n wooden sticks. For example, if you have five sticks whose pairs of length and weight are (4,9), (5,2), (2,1), (3,5), and (1,4), then the minimum setup time should be 2 minutes since there is a sequence of pairs (1,4), (3,5), (4,9), (2,1), (5,2).

 

Input

The input consists of T test cases. The number of test cases (T) is given in the first line of the input file. Each test case consists of two lines: The first line has an integer n , 1<=n<=5000, that represents the number of wooden sticks in the test case, and the second line contains n 2 positive integers l1, w1, l2, w2, ..., ln, wn, each of magnitude at most 10000 , where li and wi are the length and weight of the i th wooden stick, respectively. The 2n integers are delimited by one or more spaces.

 

Output

The output should contain the minimum setup time in minutes, one per line.

 

Sample Input

3 5 4 9 5 2 2 1 3 5 1 4 3 2 2 1 1 2 2 3 1 3 2 2 3 1

 

Sample Output

2 1 3

【题目来源】

Asia 2001, Taejon (South Korea)

【题目大意】
有一堆木棒，这些木棒的长度和重量是给定的。这些木棒将被机器一根接一根的进行处理。
机器处理每一根木棒需要一些时间，这个时间被叫做建立时间。
这个时间是这样定义的：
1.第一根木棒的建立时间是1分钟；
2.在处理一根长度为l、重量为w的木棒之后，如果木棒的l'<=l、w<=w'，那么这个机器将不需要建立时间。否则，这个机器将需要1分钟的建立时间。
你需要找到处理完这些木头的最短建立时间。题目中的例子看懂就知道怎么做了。

【题目分析】

首先按照l排序,当l相同的时候，再按照w排序，然后就是按照顺序一遍一遍的标记并统计，直至所有的都被标记，最后的count就是答案。

奇怪的是，我的代码在测试样例的时候是错的，我提交后竟然ac了。

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
struct Node
{
    int l,w;
    bool mark;
};

bool cmp(Node a,Node b)
{
    if(a.l==b.l)
    {
        return a.w<b.w;
    }
    else return a.l<b.l;
}

Node node[5050];
int main()
{
    int T;
    scanf("%d",&T);
    while(T--)
    {
        int n,i,j;
        scanf("%d",&n);
        for(i=0;i<n;i++)
        {
            scanf("%d%d",&node[i].l,&node[i].w);
            node[i].mark=0;
        }
        sort(node,node+n,cmp);
        int cl=node[0].l,cw=node[0].w;
        node[0].mark=1;
        int cnt=1;
        for(i=1;i<n;i++)
        {
            for(j=i;j<n;j++)
            {
                if(!node[j].mark&&node[j].l>=cl&&node[j].w>=cw)
                {
                    node[j].mark=1;
                    cl=node[j].l;
                    cw=node[j].w;
                }
            }
            j=1;
            while(node[j].mark)
                j++;
            i=j;
            if(i==n)
                break;
            cnt++;
            node[i].mark=1;
            cl=node[i].l;
            cw=node[i].w;
        }
        printf("%d
",cnt);
    }
    return 0;
}