Wooden Sticks

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.

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

就是利用贪心，学长那句话，说是贪心，90%会用到排序，我们对数据进行排序，我们只需要按照一个维度进行排序。然后利用另外一个维度进行比较就好了。刚才写的时候，有几个小问题，就是vis了之后，我们应不应该直接删的问题，我们应该删掉，因为这个树枝本应该被拿走，它很有可能就导致了后面本来能删除的不能删除了。所以还是说，模拟一步是一步，不要总是图省事，不写vis的话，他就不对。

#include<iostream>#include<cstdio>#include<algorithm>#include<cstring>using namespace std;typedef long long ll;const int maxn=5000+10;struct sti{    int len,weg;}s[maxn];int cmp(sti a,sti b){    if(a.len==b.len)        return a.weg <= b.weg;    return a.len <= b.len;}int vis[maxn];int main(){    int T;    scanf("%d",&T);    while(T--)    {        int n;        memset(vis,0,sizeof(vis));        memset(s,0,sizeof(s));        scanf("%d",&n);        for(int i=0;i<n;i++)        {            scanf("%d %d",&s[i].len,&s[i].weg);        }        sort(s,s+n,cmp);        int ans=0;        for(int i=0;i<n;i++)        {           if(!vis[i])           {               ans++;               vis[i]=1;               int st_w=s[i].weg;               for(int j=i+1;j<n;j++)               {                   int we=s[j].weg;                   if(!vis[j]&&we>=st_w)                   {                       vis[j]=1;                       st_w=we;                   }               }           }        }        printf("%d\n",ans);    }    return 0;}