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>
#define H 50000000
int A[H],size = 0;
int left(int);
int right(int);
int parent(int);
void maxHeapify(int);
void buildMaxHeap();
void insert(int);
int extract(void);
void increase(int);
int main() {
	int key,n = 0,j,ex[2000000],a;
	char com[20];
	while (1) {
		scanf("%s", com);
		if ('i' == com[0]) {
			scanf("%d", &key);
			insert(key);
		}
		else if ('e' == com[0] && com[1] == 'x') {
			ex[n++] = extract();
		}
		else if (com[0] == 'e' && com[1] == 'n') {
			break;
		}
	}
	for (j = 0; j < n;j++) {
		printf("%d\n",ex[j]);
	}
}
int left(int i) {
	return 2 * i;
}
int right(int i) {
	return 2 * i + 1;
}
int parent(int i) {
	return i / 2;
}
void maxHeapify(int i) {
	int swap;
	int largest, r, l;
	r = right(i);
	if (r > size) {
		A[r] = -2000000001;
	}
	l = left(i);
	if (l <= size && A[l] > A[i]) {
		largest = l;
	}
	else {
		largest = i;
	}
	if (r <= size && A[r] > A[largest]) {
		largest = r;
	}
	if (largest != i) {
		swap = A[i];
		A[i] = A[largest];
		A[largest] = swap;
		maxHeapify(largest);
	}
}
void buildMaxHeap() {
	int i;
	for (i = size / 2; i > 0; i--) {
		maxHeapify(i);
	}
}
void insert(int k) {
	size++;
	A[size] = k;
	increase(k);
}
void increase(int k) {
	int swap,i;
	i = size;
	while(i > 1 && A[parent(i)] < A[i]){
		swap = A[i];
		A[i] = A[parent(i)];
		A[parent(i)] = swap;
		i = parent(i);
	}
}
int extract() {
	int max;
	max = A[1];
	A[1] = A[size];
	size--;
	maxHeapify(1);
	return max;
}