Description
A restaurant received n orders for the rental. Each rental order reserve the restaurant for a continuous period of time, the i-th order is characterized by two time values — the start time li and the finish time ri (li ≤ ri).
Restaurant management can accept and reject orders. What is the maximal number of orders the restaurant can accept?
No two accepted orders can intersect, i.e. they can't share even a moment of time. If one order ends in the moment other starts, they can't be accepted both.
Input
The first line contains integer number n (1 ≤ n ≤ 5·105) — number of orders. The following n lines contain integer values li and ri each (1 ≤ li ≤ ri ≤ 109).
Output
Print the maximal number of orders that can be accepted.
Examples
input
2
7 11
4 7
output
1
input
5
1 2
2 3
3 4
4 5
5 6
output
3
input
6
4 8
1 5
4 7
2 5
1 3
6 8
output
2
贪心，求最多的不相交线段
#include<bits/stdc++.h>
using namespace std;
struct P
{
int s,e;
}He[5*100000];
bool cmd(P x,P y)
{
return x.e<y.e;
}
int main()
{
int n;
cin>>n;
for(int i=0;i<n;i++)
{
cin>>He[i].s>>He[i].e;
}
sort(He,He+n,cmd);
int sum=He[0].e;
int pos=1;
for(int i=0;i<n;i++)
{
if(He[i].s>sum)
{
sum=He[i].e;
pos++;
}
}
cout<<pos<<endl;
return 0;
}