C :

#include<stdio.h>
int n,begin[1000],end[1000],a[1000],k;
int main()
{
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
	scanf("%d %d",&begin[i],&end[i]);
	for(int i=1;i<n;i++)
	for(int j=i+1;j<=n;j++)
	if(end[i]>end[j])
	{
		int t1=begin[i],t2=end[i];
		begin[i]=begin[j];
		begin[j]=t1;
		end[i]=end[j];
		end[j]=t2;
	}
	int endx=0;
	for(int i=1;i<=n;i++)
	if(begin[i]>=endx)
	{
		endx=end[i];
		k++;
	}
	printf("%d",k);
	return 0;
}

C++ :

#include<iostream>
using namespace std;
int n,b[1001],e[1001];
void solve()
{ 
  int ans=0;
  int t = -1;
  for(int i=1;i<=n;++i)     
   //如果当前活动与之前最后结束的活动不冲突，就接受当前活动。
   if(b[i]>=t) {
      ++ans;
	  t=e[i];
   }
  cout<<ans<<endl;
}
int main()
{
  int i,j,t;
  cin>>n;
  for(i=1;i<=n;i++) 
     cin>>b[i]>>e[i];
  //按照结束时间对2个数组同时排序
  for(i = 1;i < n;i++){
  	  for(j = 1;j <= n - i;j++){
  		   if(e[j] > e[j+1]){
  		     swap(e[j],e[j+1]);
			 swap(b[j],b[j+1]);	
		   }
	  }
  }
   
  solve();
  return 0;
}

Java :

import java.util.Arrays;
import java.util.Comparator;
import java.util.Scanner;

public class Main {


	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt(),i;
		//节点数组
		Node[] nodes = new Node[n];
		for(i=0;i<n;i++) {
			nodes[i] = new Node();
			nodes[i].begin = sc.nextInt();
			nodes[i].end = sc.nextInt();
		}
		
		Arrays.sort(nodes,new Comparator<Node>() {
			@Override
			public int compare(Node a, Node b) {
				if(a.end < b.end) return -1;
				else return 1;
			}
		});
		
		int end = nodes[0].end;
		int c = 1;
		for(i=1;i<n;i++){
	   		//如果当前的开始时间 >=上一个活动的结束时间 
	   		if(nodes[i].begin >= end){
				c++;
				end = nodes[i].end;   
			} 
	   } 
		System.out.println(c);
		sc.close();
	}
	
}

class Node{
	int begin;
	int end;
}

Python :

n=int(input())
a=[[0 for i in range(2)] for j in range(n)]
for i in range(n):
    sr=input().split()
    a[i][0]=int(sr[0])
    a[i][1]=int(sr[1])
for i in range(n-1):
    for j in range(n-i-1):
        if(a[j][1]>a[j+1][1]):
            t=a[j][0]
            a[j][0]=a[j+1][0]
            a[j+1][0]=t
            t=a[j][1]
            a[j][1]=a[j+1][1]
            a[j+1][1]=t
c=[]
c.append(a[0][1])
k=0
for i in range(1,n):
    if(a[i][0]>=c[k]):
        k=k+1
        c.append(a[i][1])
print(k+1)