HDU 1025 Constructing Roads In JGShining's Kingdom

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
struct P
{
int x,y;
};
bool comp(P a, P b)
{
return a.x<b.x;
}
int dp[500100];
P a[500100];
int main()
{
int n ,flag =1;
while(~scanf("%d",&n))
{
for(int i = 0 ; i < n ; i++)
{
scanf("%d%d",&a[i].x,&a[i].y);
}
memset(dp,0,sizeof(0));
sort(a,a+n,comp);
int j,k;
j = 0;
for(int i = 0 ; i < n ; i++)
{
for(k = j ; k >=0 ; k--)
{
if(dp[k]<a[i].y)
{
dp[++k] = a[i].y;
break;
}
}
j = max (j,k);
}
printf("Case %d:\n",flag++);
if(j == 1) printf("My king, at most 1 road can be built.\n\n");
else printf("My king, at most %d roads can be built.\n\n",j);
}
return 0;
}