cf Ping-Pong (Easy Version)

http://codeforces.com/contest/320/problem/B

这道题看了很长时间没看懂, 就是个dfs；

 #include <cstdio>
 #include <cstring>
 #define maxn 2000
 using namespace std;

 int a[maxn],b[maxn];
 bool vis[maxn];
 int cnt=;

 bool dfs(int x,int y)
 {
     vis[x]=true;
     if(x==y) return ;
     for(int i=; i<=cnt; i++)
     {
         if(!vis[i]&&((a[i]<a[x]&&a[x]<b[i])||(a[i]<b[x]&&b[x]<b[i])))
         {
             if(dfs(i,y)) return true;
         }
     }
     return false;
 }

 int main()
 {
     int n,x,y,c;
     scanf("%d",&n);
     memset(vis,false,sizeof(vis));
     for(int i=; i<=n; i++)
     {
         scanf("%d%d%d",&c,&x,&y);
         if(c==)
         {
             a[cnt]=x; b[cnt++]=y;
         }
         else
         {
             memset(vis,false,sizeof(vis));
             if(!dfs(x,y)) printf("NO\n");
             else printf("YES\n");
         }
     }
     return ;
 }