Problem:
MathJax.Hub.Config({ tex2jax: { inlineMath: [["$","$"], ["\\(","\\)"]], processEscapes: true }});

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)

#include <stdio.h>          // printf(), scanf(), getc(), ungetc()
#include <ctype.h>          // isdigit()
#include <stdbool.h>

#define MAX_N 2000000
#define swap(a, b) { int t; t = a; a = b; b = t; }

const int INF = (1 << 30);
int a[MAX_N + 1];
int h;

void
max_heapify(int i)
{
	int largest;

	int l = 2 * i;
	int r = 2 * i + 1;

	/* ????????????????????????????????§???????????§???node????????¶ */
	if (l <= h && a[l] > a[i])
		largest = l;
	else
		largest = i;

	if (r <= h && a[r] > a[largest])
		largest = r;

	if (largest != i) /* ????????????????????§????????´?????? */
	{
		swap(a[i], a[largest]);
		max_heapify(largest);
	}
}

int
extract()
{
	if (h < 1)
		return -INF;

	int maxv = a[1];
	a[1] = a[h--];
	max_heapify(1);
	return maxv;
}

void
increase_key(int i, int key)
{
	if (key < a[i])
		return;

	a[i] = key;
	while (i > 1 && a[i / 2] < a[i])
	{
		swap(a[i], a[i / 2]);
		i /= 2;
	}
}

void
insert(int key)
{
	h++;
	a[h] = -INF;
	increase_key(h, key);
}

int
main(int argc, char** argv)
{
	char command[8];
	int key;
	int n;
	int c;

	h = 0;
	while (true)
	{
		scanf("%s", command);
		if (command[0] == 'e' && command[1] == 'n')
			break;

		else if (command[0] == 'e' && command[1] == 'x')
			printf("%d\n", extract());

		else if (command[0] == 'i')
		{
			n = 0;
			c = getc(stdin);
			while (c == ' ' || c == '\n')
				c = getc(stdin);
			
			while (isdigit(c))
			{
				n = 10 * n + c - '0';
				c = getc(stdin);
			}

			ungetc(c, stdin);
			key = n;
			insert(key);
		}
	}

	return 0;
}