HDU1051 Wooden Sticks

Wooden Sticks

                                                                      Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)

                                                                      Total Submission(s): 20528    Accepted Submission(s): 8309

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

213

 

Source

Asia 2001, Taejon (South Korea)

思路：贪心问题，求所给数据中递增子序列的个数。

首先按木棍长度从小到大排列，在长度相同时按重量排，最后问最少的序列有几个？

#include<stdio.h>#include<algorithm>#include<iostream>using namespace std;struct stick{    int len;    int wei;};int cmp(stick a,stick b){    if(a.len==b.len)        return a.wei<b.wei;    return a.len<b.len;//贪心}int main(){    int t;    stick a[5005],w;    cin>>t;    while(t--)    {        int n,i,j;        int flag[5005]={0};        cin>>n;        for(i=0;i<n;i++)            cin>>a[i].len>>a[i].wei;        sort(a,a+n,cmp);        int ants=0;        for(i=0;i<n;i++)        {            w.wei=a[i].wei;//作为每个序列的第一个元素            if(!flag[i])            {               for(j=i+1;j<n;j++)               {                   if(w.wei<=a[j].wei&&!flag[j])                   {                       flag[j]=1;//元素已被使用                       w.wei=a[j].wei;//更新当前的                   }               }               ants++;            }        }        cout<<ants<<endl;    }    return 0;}