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<string.h>
#define MAX 2000000
#define MIN -1

void maxHeapify(int *,int);
int heapExtractMax(void);
void heapIncreaseKey(int *,int,int);
void insert(int);


int H, a[MAX+1];
int main(){
  int n;
  char com[20];
  
  while(1){
    scanf("%s", com);
    if ( com[0] == 'e'&&com[1]=='n' ) break;
    if(com[0]=='i'){
      scanf("%d", &n);
      insert(n);
    } else {
      printf("%d\n",heapExtractMax());
    }
  }
  
  return 0;
}

void maxHeapify(int a[],int i){
  int l, r, largest, x;
  l = 2*i;
  r = 2*i+1;
  if ( l <= H && a[l] > a[i] ){
    largest = l;
  }
  else {
    largest = i;
  }
  if ( r <= H && a[r] > a[largest] ) {
    largest = r;
  }
  if ( largest != i ){
    x = a[i];
    a[i] = a[largest];
    a[largest] = x;
    maxHeapify(a,largest);
  }
}

int heapExtractMax(){
  int x;
  if ( H < 1 ) return MIN;
  x = a[1];
  a[1] = a[H];
  H--;
  maxHeapify(a,1);
  return x;
}

void heapIncreaseKey(int a[],int i, int n){
  int y;
  if ( n < a[i] ) return;
  a[i] = n;
  while ( i > 1 && a[i/2] < a[i] ){
    y = a[i];
    a[i] = a[i/2];
    a[i/2] = y;
    i = i/2;
  }
}

void insert(int n){
  H++;
  a[H] = -100000000000;
  heapIncreaseKey(a,H,n);
}