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;

namespace ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
			var que = new PriorityQueue<int>(2000000, 1);
			while (true) {
				var input = Console.ReadLine().Split(' ').ToArray();
				if (input[0] == "end") Environment.Exit(0);
				if (input[0][0] == 'i') {
					que.Push(int.Parse(input[1]));
				} else {
					Console.WriteLine(que.Pop());
				}
			}	
        }
    }

	public class PriorityQueue<T> where T : IComparable
	{
		private IComparer<T> _comparer = null;
		private int _type = 0;

		private T[] _heap;
		private int _sz = 0;

		private int _count = 0;

		/// <summary>
		/// Priority Queue with custom comparer
		/// </summary>
		public PriorityQueue(int maxSize, IComparer<T> comparer)
		{
			_heap = new T[maxSize];
			_comparer = comparer;
		}

		/// <summary>
		/// Priority queue
		/// </summary>
		/// <param name="maxSize">max size</param>
		/// <param name="type">0: asc, 1:desc</param>
		public PriorityQueue(int maxSize, int type = 0)
		{
			_heap = new T[maxSize];
			_type = type;
		}

		private int Compare(T x, T y)
		{
			if (_comparer != null) return _comparer.Compare(x, y);
			return _type == 0 ? x.CompareTo(y) : y.CompareTo(x);
		}

		public void Push(T x)
		{
			_count++;

			//node number
			var i = _sz++;

			while (i > 0) {
				//parent node number
				var p = (i - 1) / 2;

				if (Compare(_heap[p], x) <= 0) break;

				_heap[i] = _heap[p];
				i = p;
			}

			_heap[i] = x;
		}

		public T Pop()
		{
			_count--;

			T ret = _heap[0];
			T x = _heap[--_sz];

			int i = 0;
			while (i * 2 + 1 < _sz) {
				//children
				int a = i * 2 + 1;
				int b = i * 2 + 2;

				if (b < _sz && Compare(_heap[b], _heap[a]) < 0) a = b;

				if (Compare(_heap[a], x) >= 0) break;

				_heap[i] = _heap[a];
				i = a;
			}

			_heap[i] = x;

			return ret;
		}

		public int Count()
		{
			return _count;
		}

		public T Peek()
		{
			return _heap[0];
		}

		public bool Contains(T x)
		{
			for (int i = 0; i < _sz; i++) if (x.Equals(_heap[i])) return true;
			return false;
		}

		public void Clear()
		{
			while (this.Count() > 0) this.Pop();
		}

		public IEnumerator<T> GetEnumerator()
		{
			var ret = new List<T>();

			while (this.Count() > 0) {
				ret.Add(this.Pop());
			}

			foreach (var r in ret) {
				this.Push(r);
				yield return r;
			}
		}

		public T[] ToArray()
		{
			T[] array = new T[_sz];
			int i = 0;

			foreach (var r in this) {
				array[i++] = r;
			}

			return array;
		}
	}
}