Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 10423 Accepted Submission(s): 4287

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

4 9 5 2 2 1 3 5 1 4

2 1 1 2

1 3 2 2 3 1

Sample Output

Source

Asia 2001, Taejon (South Korea)

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　　水题。

　　先对木材长度 l 排序，在对 w 依次处理，将第一个递增序列筛选出来，筛选出来的元素赋值为-1，再将第二个递增序列筛选出来，同样标记-1 ，直到w序列全部为-1，代表筛选完成。输出记录下的递增序列的个数就是结果。

　　还可以用贪心做，有时间再做一遍。

　　代码：

 #include <iostream>

 using namespace std;

 struct stick{

     int l,w;

 }s[];

 int main()

 {

     int T;

     cin>>T;

     while(T--){

         int n;

         cin>>n;

         for(int i=;i<=n;i++)

             cin>>s[i].l>>s[i].w;

         //对l排序

         for(int i=;i<=n-;i++)

             for(int j=;j<=n-i;j++){

                 if(s[j].l>s[j+].l){

                     int t;

                     t=s[j].l;s[j].l=s[j+].l;s[j+].l=t;

                     t=s[j].w;s[j].w=s[j+].w;s[j+].w=t;

                 }

             }

         int sum=;  //递增序列的个数

         //对w序列进行筛选

         while(){

             int i;

             for(i=;i<=n;i++){  //如果全部为-1，则退出循环

                 if(s[i].w!=-)

                     break;

             }

             if(i>n) break;

             sum++;

             int num=;

             for(i=;i<=n;i++){

                 if(num== && s[i].w!=-){

                     num=s[i].w;

                     s[i].w=-;

                 }

                 else if(s[i].w!=- && s[i].w>=num){

                     num=s[i].w;

                     s[i].w=-;

                 }

             }

         }

         cout<<sum<<endl;

     }

     return ;

 }

Freecode : www.cnblogs.com/yym2013

巴特西

hdu 1051:Wooden Sticks（水题，贪心）

Wooden Sticks

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