线段覆盖（动态规划）

http://wikioi.com/problem/1214/

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<bitset>
#include<iomanip>

using namespace std;
#define maxn 1005 
int dp[ maxn ] ;
struct node
{
	int left , right , value ;
}edge[ maxn ] ;

int cmp( const node a , const node b )
{
	return a.right < b.right ;
}

int main()
{
	int n ;
	scanf( "%d" , &n ) ;
	{
		memset( edge , 0 , sizeof( edge ) ) ; 
		for( int i = 1 ; i <= n ; ++i )
		{
			scanf( "%d  %d" , &edge[ i ].left , &edge[ i ].right ) ;
			if( edge[ i ].left > edge[ i ].right )
			{
				int temp = edge[ i ].left ;
				edge[ i ].left = edge[ i ].right ;
				edge[ i ].right = temp ;
			}
		}
		sort( edge + 1 , edge + n + 1 , cmp ) ;
		edge[ 1 ].value = 1 ;
		for( int i = 2 ; i <= n ; ++i )
		{
			for( int j = 1 ; j <= i - 1 ; ++j )
			{
				if( edge[ i ].left >= edge[ j ].right )
				{ 
					edge[ i ].value = max( edge[ i ].value , edge[ j ].value + 1 ) ;
				}		
			} 
		}
		
		int Max = 0 ;
		for( int i = 1 ; i <= n ; ++i )
		{
			 
			if( Max < edge[ i ].value )
				Max = edge[ i ].value;
		} 
		printf( "%d\n" , Max ) ;
	}
	return 0 ;
}