Wooden Sticks

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

#include <stdio.h>
#include <string.h>
#include <algorithm>
#define maxn 5002
using std::sort;

struct Node{
	int l, w;
} arr[maxn];
bool vis[maxn];

bool cmp(Node a, Node b){
	if(a.l == b.l) return a.w < b.w;
	return a.l < b.l;
}

int main()
{
//	freopen("stdin.txt", "r", stdin);
	int t, n, i, j, ans;
	Node tmp;
	scanf("%d", &t);
	while(t--){
		scanf("%d", &n);
		for(i = 0; i < n; ++i)
			scanf("%d%d", &arr[i].l, &arr[i].w);
		sort(arr, arr + n, cmp);
		memset(vis, 0, sizeof(vis));
		for(i = 0, ans = n; i < n; ++i){
			if(vis[i]) continue;
			vis[i] = 1; tmp = arr[i];
			for(j = i + 1; j < n; ++j){
				if(vis[j]) continue;
				if(tmp.l <= arr[j].l && tmp.w <= arr[j].w){
					vis[j] = 1;
					--ans; tmp = arr[j];
				}
			}
		}
		printf("%d\n", ans);
	}
	return 0;
}