Problem:
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Priority Queue

A priority queue is a data structure which maintains a set $S$ of elements, each of with an associated value (key), and supports the following operations:

$insert(S, k)$: insert an element $k$ into the set $S$

$extractMax(S)$: remove and return the element of $S$ with the largest key

Write a program which performs the $insert(S, k)$ and $extractMax(S)$ operations to a priority queue $S$.
The priority queue manages a set of integers, which are also keys for the priority.

Input

Multiple operations to the priority queue $S$ are given. Each operation is given by "insert $k$", "extract" or "end" in a line. Here, $k$ represents an integer element to be inserted to the priority queue.

The input ends with "end" operation.

Output

For each "extract" operation, print the element extracted from the priority queue $S$ in a line.

Constraints

The number of operations $\leq 2,000,000$

$0 \leq k \leq 2,000,000,000$

Sample Input 1

insert 8
insert 2
extract
insert 10
extract
insert 11
extract
extract
end

Sample Output 1

8
10
11
2

Solution in C# (judge verdict: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using CompProgLib;

namespace ALDS1_9_C
{
    public class Program

    {
        public static void Main(string[] args)
        {
            PriorityQueue<int> pq = new PriorityQueue<int>();
            string[] line;
            while (true)
            {
               line = ReadStAr();

                switch (line[0])
                {
                    case "end":
                        return;
                    case "insert":
                        pq.Enqueue(int.Parse(line[1]));
                        break;
                    case "extract":
                        Console.WriteLine(pq.Dequeue().ToString());
                        break;
                }
            }
        }

        static string ReadSt() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Console.ReadLine()); }
        static long ReadLong() { return long.Parse(Console.ReadLine()); }
        static double ReadDouble() { return double.Parse(Console.ReadLine()); }
        static string[] ReadStAr(char sep = ' ') { return Console.ReadLine().Split(sep); }
        static int[] ReadIntAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => int.Parse(e)); }
        static long[] ReadLongAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => long.Parse(e)); }
        static double[] ReadDoubleAr(char sep = ' ') { return Array.ConvertAll(Console.ReadLine().Split(sep), e => double.Parse(e)); }

    }

}

namespace CompProgLib
{
    public class PriorityQueue<T> where T : IComparable<T>

    {

        private List<T> Buffer { get; set; }

        public int Count { get { return Buffer.Count; } }

        public PriorityQueue() { Buffer = new List<T>(); }
        public PriorityQueue(int capacity) { Buffer = new List<T>(capacity); }


        /// <summary>
        /// ヒープ化されている配列リストに新しい要素を追加する。
        /// </summary>
        public void Enqueue(T item)
        {
            int n = Buffer.Count;
            Buffer.Add(item);

            while (n != 0)
            {
                int i = (n - 1) / 2;
                if (Buffer[n].CompareTo(Buffer[i]) > 0)
                {
                    T tmp = Buffer[n]; Buffer[n] = Buffer[i]; Buffer[i] = tmp;
                }
                n = i;
            }
        }

        /// <summary>
        /// ヒープから最大値を削除する。
        /// </summary>
        public T Dequeue()
        {
            T ret = Buffer[0];
            int n = Buffer.Count - 1;
            Buffer[0] = Buffer[n];
            Buffer.RemoveAt(n);

            for (int i = 0, j ; (j = 2 * i + 1) < n ;)
            {
                if ((j != n - 1) && (Buffer[j].CompareTo(Buffer[j + 1]) < 0))
                    j++;
                if (Buffer[i].CompareTo(Buffer[j]) < 0)
                {
                    T tmp = Buffer[j]; Buffer[j] = Buffer[i]; Buffer[i] = tmp;
                }
                i = j;
            }
            return ret;
        }

        public T Peek()
        {
            if (Count == 0) throw new InvalidOperationException();
            return this.Buffer[0];
        }
    }
}