HDU 1051： Wooden Sticks（贪心）

Posted 2020-09-22 wzjhoutai

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 11244    Accepted Submission(s): 4627

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

题意是第一个3是3组数据， 然后一个5是5根棍子。 然后逐一输入其的长度和重量。

。题目是问怎么做这些棍子用时最少，在做棍子时。若后一根棍子。长度和重量都大于前

一根。则不用加时间。。

想法。。

拿第一组数据来说。

。

首先按长度以小到大排序：（1,4），（2，1），（3。 5）。 （4， 9），（5,2）；

我们发现（2。 1）的重量太小， 而（5， 2）的长度太长。这样排结果为3；

事实上这时，我们仅仅要把不满足的先标记起来。

。

则（1,4）。（3,5），（4,9）      ————     （2,1）， （5,2）

但我们这么排， 也就是题目给出的顺序，结果就为2；也就是最优。

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<vector>
#include<queue>
#include<sstream>
#include<cmath>

using namespace std;

#define M 100500

struct node
{
    int lenth;
    int weight;
    int k;
} Q[M];

bool cmp ( node a, node b )
{
    if(a.lenth==b.lenth)
        return a.weight<b.weight;
    else
        return a.lenth<b.lenth;
}

int main()
{
    int t;
    int n;
    scanf("%d", &t);
    while( t-- )
    {
        scanf("%d", &n);
        for(int i=0; i<n; i++)
        {
            scanf("%d%d", &Q[i].lenth, &Q[i].weight);
            Q[i].k= 1;
        }
        sort( Q, Q+n, cmp );
        int ans = 0;
        for(int i=0; i<n-1; i++)
        {
            if(!Q[i].k)
                continue;
            int t = Q[i].weight;
            for(int j = i+1; j<n; j++)
                if(Q[j].weight>=t &&Q[j].k==1 )
                {
                    ans++;
                    Q[j].k=0;
                    t = Q[j].weight;
                }
        }
        printf("%d\n", n-ans);
    }

    return 0;
}