hdu1051——Wooden Sticks

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 12086    Accepted Submission(s): 5011

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
  

 

Source

Asia 2001, Taejon (South Korea)

 

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类似于会场安排问题，点有5000个， 可以贪心解决，如果点少，其实可以建图，然后dfs染色去做，求出最少用的点数

#include <set>
#include <map>
#include <list>
#include <stack>
#include <queue>
#include <vector>
#include <cmath>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 5010;

struct node
{
    int l, w;
}wood[N];
bool mark[N];

int cmp(node a, node b)
{
    if (a.l != b.l)
    {
        return a.l < b.l;
    }
    return a.w < b.w;
}

int main()
{
    int t, n;
    scanf("%d", &t);
    while (t--)
    {
        scanf("%d", &n);
        memset (mark, 0, sizeof(mark) );
        for (int i = 0; i < n; ++i)
        {
            scanf("%d%d", &wood[i].l, &wood[i].w);
        }
        sort(wood, wood + n, cmp);
        int ans = 0;
        int mark_num = 0;
        int p;
        while (mark_num < n)
        {
            for (int i = 0; i < n; ++i)
            {
                if(mark[i] == 0)
                {
                    p = i;
                    break;
                }
            }
            ans++;
            mark_num++;
            mark[p] = 1;
            for (int i = 0; i < n; ++i)
            {
                if (mark[i])
                {
                    continue;
                }
                if(wood[i].l >= wood[p].l && wood[i].w >= wood[p].w)
                {
                    mark[i] = 1;
                    mark_num++;
                    p = i;
                }
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}