【codechef】一维王国问题（最少需要几颗炸弹）

N one dimensional kingdoms are represented as intervals of the form [a_i , b_i] on the real line.
A kingdom of the form [L, R] can be destroyed completely by placing a bomb at a point x on the real line if L
≤ x ≤ R.

Your task is to determine minimum number of bombs required to destroy all the one dimensional kingdoms.

Input

First line of the input contains T denoting number of test cases.
For each test case, first line contains N denoting the number of one dimensional kingdoms.
For each next N lines, each line contains two space separated integers a_i and b_i.

Output

For each test case , output an integer denoting the minimum number of bombs required.

Constraints

Subtask 1 (20 points) : 1 ≤ T ≤ 100 , 1 ≤ N ≤ 100 , 0 ≤ a_i ≤ b_i ≤500

Subtask 2 (30 points) : 1 ≤ T ≤ 100 , 1 ≤ N ≤ 1000 , 0 ≤ a_i ≤ b_i ≤ 1000

Subtask 3 (50 points) : 1 ≤ T ≤ 20 , 1 ≤ N ≤ 10⁵, 0 ≤ a_i ≤ b_i ≤ 2000

Example

Input:
1
3
1 3
2 5
6 9

Output:
2

Explanation

There are three kingdoms [1,3] ,[2,5] and [6,9]. You will need at least 2 bombs

to destroy the kingdoms. In one of the possible solutions, you can place two bombs at x = 2 and x = 6 .

http://www.codechef.com/problems/ONEKING

int compare(pair<int,int> x,pair<int,int> y){
	return x.second<y.second;}
int main(){
	int m,n,s;
	pair<int ,int> x[100001];
	cin>>m;
	while(m--){
		int t=1;
		cin>>n;
		for(int i=0;i<n;++i)
			cin>>x[i].first>>x[i].second;
		sort(x,x+n,compare);
		s=0;
		for(int i=1;i<n;++i){
			if(x[i].first>x[s].second){
				t++;
				s=i;}}
		cout<<t<<endl;}
	return 0;
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