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)

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int n;

int parent(int i) {
	return i / 2;
}

int left(int i) {
	return 2 * i;
}

int right(int i) {
	return 2 * i + 1;
}

void swap(int *x, int *y) {
	int tmp;

	tmp = *x;
	*x = *y;
	*y = tmp;
}

void maxHeapify(int *A, int i) {
	int l, r, largest;

	l = left(i);
	r = right(i);

	if (l <= n && A[l] > A[i]) largest = l;
	else largest = i;

	if (r <= n && A[r] > A[largest]) largest = r;
	if (largest != i) {
		swap(&A[i], &A[largest]);
		maxHeapify(A, largest);
	}
}

void heapIncreaseKey(int *A, int i, int key) {
	if (key >= A[i]) {
		A[i] = key;
		while (i > 1 && A[parent(i)] < A[i]) {
			swap(&A[i], &A[parent(i)]);
			i = parent(i);
		}
	}
}

void maxHeapInsert(int *A, int key) {
	n++;
	A[n] = -32768;
	heapIncreaseKey(A, n, key);
}

int heapExtractMax(int *A) {
	int max;

	if (n >= 1) {
		max = A[1];
		A[1] = A[n];
		n--;
		maxHeapify(A, 1);
		return max;
	}

	return -1;
}

main() {
	int *node;
	int key;
	char order[8];

	node = (int*)malloc(sizeof(int) * 2000000);

	while (1) {
		scanf("%s", &order);
		if (!strcmp(order, "insert")) {
			scanf("%d", &key);
			maxHeapInsert(node, key);
		}
		else if (!strcmp(order, "extract")) printf("%d\n", heapExtractMax(node));
		else if (!strcmp(order, "end")) break;
	}

	free(node);

	return 0;
}