POJ 1442(treap || 优先队列)

treap套用模板即可：

#include <iostream>
#include <cstdio>
#include <cstdlib>
using namespace std;
#define maxn 30000+5
int m,n;
int a[maxn],b[maxn];
int val[maxn],ch[maxn][2],r[maxn],size[maxn],root,cnt,counts[maxn];
inline void pushup(int rt)
{
  size[rt] = size[ch[rt][0]] + size[ch[rt][1]] + counts[rt];
}
void rotate(int &x,int kind)
{
  int y = ch[x][kind^1];
  ch[x][kind^1] = ch[y][kind];
  ch[y][kind] = x;
  pushup(x);
  pushup(y);
  x = y;
}
void newnode(int &rt, int v)
{
   rt = ++ cnt;
   val[rt] = v;
   ch[rt][0] = ch[rt][1] = 0;
   size[rt] = counts[rt] = 1;
   r[rt] = rand();
}
void insert(int &rt, int v)
{
  if(rt == 0)
  {
    newnode(rt, v);
    return;
  }
  if(val[rt] == v)
  counts[rt] ++;
  else
  {
	int kind = (val[rt] < v);
	insert(ch[rt][kind], v);
	if(r[ch[rt][kind]] < r[rt])
	rotate(rt, kind^1);
  }
  pushup(rt);
}
int select(int rt,int k)
{
  if(size[ch[rt][0]] >= k) return select(ch[rt][0], k);
  if(size[ch[rt][0]] + counts[rt] >= k) return val[rt];
  return select(ch[rt][1], k - size[ch[rt][0]] - counts[rt]);
}
int main()
{
     root = 0;
	 cnt = 0;
	 while(scanf("%d%d",&n,&m) != EOF)
	 {
	 for(int i = 1;i <= n;i ++)
	 scanf("%d", &a[i]);
	 for(int j = 1;j <= m;j ++)
	 scanf("%d", &b[j]);
	 int k = 1;
	 for(int i = 1;i <= n;i ++)
	 {
	   insert(root, a[i]);
	   if(k > n) break;
	   while(b[k] == i)
	   {
         printf("%d\n",select(root, k));
		 k ++;
	   }
	 }
	 }
	 return 0;
}

也可以使用优先队列来做，维护两个优先队列~

#include <iostream>
#include <cstdio>
#include <queue>
#include <vector>
using namespace std;
#define maxn 30000 + 5
int main()
{
    int n, m;
    priority_queue<int, vector<int>, greater<int> > q1;
    priority_queue<int, vector<int>, less<int> > q2;
    int a[maxn],b[maxn];
    while(scanf("%d%d",&n, &m) != EOF)
    {
      while(!q1.empty())
      q1.pop();
      while(!q2.empty())
      q2.pop();
      for(int i = 1;i <= n;i ++)
      {
        scanf("%d", &a[i]);
      }
      for(int j = 1;j <= m;j ++)
      {
        scanf("%d", &b[j]);
      }
      int k = 1;
      for(int i = 1;i <= n;i ++)
      {
        if(!q1.empty())
        {
          if(a[i] < q1.top())
          q2.push(a[i]);
          else
          {
           q2.push(q1.top());
           q1.pop();
           q1.push(a[i]);
          }
        }
        else q2.push(a[i]);
        while(b[k] == i)
        {
          if(q2.size() == k)
          {
            printf("%d\n",q2.top());
          }
          else if(q2.size() > k)
          {
            while(q2.size() != k)
            {
              q1.push(q2.top());
              q2.pop();
            }
            printf("%d\n",q2.top());
          }
          else if(q2.size() < k)
          {
            while(q2.size() != k)
            {
              q2.push(q1.top());
              q1.pop();
            }
            printf("%d\n",q2.top());
          }
          k++;
        }
      }
    }
    return 0;
}

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