HDU 1051 Wooden Sticks

Wooden Sticks

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 22142    Accepted Submission(s): 8902

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)

/*
* @Author: Lyucheng
* @Date:   2017-07-19 10:34:05
* @Last Modified by:   Lyucheng
* @Last Modified time: 2017-07-19 12:31:05
*/
/*
 题意：有n个木棍，长宽给出，机器加工木棍，第一个木棍需要一分钟，如果接下来的木棍l'>=l并且w'>=l那么这个
    木棍就不需要时间，问你最短时间多少
 思路：排序，然后贪心

 错误：理解错题意了，下边有解释
*/
#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>

#define MAXN 5005

using namespace std;

struct Node {
    int x,y;
    bool operator < (const Node & other) const{
        if(x==other.x) return y<other.y;
        return x<other.x;
    }
}node[MAXN];
bool vis[MAXN];
int n;
int t;
int res;

inline void init(){
    res=0;
    memset(vis,false,sizeof vis);
}

int main(){
    // freopen("in.txt", "r", stdin);
    // freopen("out.txt", "w", stdout);
    scanf("%d",&t);
    while(t--){
        init();
        scanf("%d",&n);
        for(int i=1;i<=n;i++){
            scanf("%d%d",&node[i].x,&node[i].y);
        }
        sort(node+1,node+n+1);//按照x从小到大排序
        for(int i=1;i<=n;i++){
            if(vis[i]==true) continue;
            res++;
            int pos=node[i].y;
            for(int j=i+1;j<=n;j++){
                if(vis[j]==true) continue;
                else {
                    // if(node[j].y>=node[i].y){//这么比较是错的，题意是说你切完一根了，下一根以上一根为准                    
                    //     vis[j]=true;
                    // }
                    if(node[j].y>=pos){
                        vis[j]=true;
                        pos=node[j].y;
                    }
                }
            }
        }
        printf("%d
",res);
    }  
    return 0;
}