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>

int A[2000001], H=1;

void swap(int a, int b){
  int temp=0;

  temp = A[a];
  A[a] = A[b];
  A[b] = temp;
}

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

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

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

void insert(int i){
  int p = parent(i);
  if(p == 0) return;

  if(A[i] > A[p]) {
    swap(i, p);
    insert(p);
  }
}

void extract(int i){
  int l = left(i);
  int r = right(i);
  int largest;

  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(i, largest);
    extract(largest);
  }
}

void printer(){
    for(int i=1; i<H; i++){
      printf("%d ",A[i]);
    }
    puts("");
}

int main(){
  char cmd[10];

  while(scanf("%s ",cmd) != EOF){
    if(!strcmp(cmd, "end")) break;
    else if(!strcmp(cmd, "extract")) {
      printf("%d\n",A[1]);
      A[1] = A[--H];
      extract(1);
    } else {
      scanf("%d ",&A[H]);
      insert(H++);
    }
    // printf("%s\n",cmd);
    // printer();
  }
  return 0;
}