Wooden Sticks

题目
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 ( 9 , 4 ) , ( 2 , 5 ) , ( 1 , 2 ) , ( 5 , 3 ) , and ( 4 , 1 ) , then the minimum setup time should be 2 minutes since there is a sequence of pairs ( 4 , 1 ) , ( 5 , 3 ) , ( 9 , 4 ) , ( 1 , 2 ) , ( 2 , 5 )
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 2n 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.

simple 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

simple output

2
1
3

思路：先用sort按length从小到大排序，再按weight从小到大选择

AC代码：

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;

const int maxn = 5000+10;

struct node
{
    int length;
    int weight;
    bool vis;
};

node a[maxn];
bool cmp(node x,node y){
    return x.length<y.length;
}


int main(){
    int t;
    int n;
    cin>>t;
    while(t--){
        int ans=0;
        cin>>n;
        for(int i=0;i<n;i++){
            scanf("%d%d",&a[i].length,&a[i].weight);
            a[i].vis=false;
        }
        sort(a,a+n,cmp);
        
        while(1){
            int flag=0;
            int start=0;
            for(int i=0;i<n;i++){
                if(a[i].vis==false){
                    start=i;
                    flag=1;
                    ans++;
                    break;
                }
            }
            if(flag==0){
                break;
            }
            else{
                int x=start;
                for(int i=start;i<n;i++){
                    if(a[x].weight<=a[i].weight&&a[i].vis==false){
                        a[i].vis=true;
                        x=i;
                    }
                }
            }
        }
        cout<<ans<<endl;
    }




}代码片