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 N 200000000
#define INF 2000000001
 
int size;
int heap[N];
 
void swap(int* a, int* b){
  int tmp = *a;
  *a = *b;
  *b = tmp;
}
 
void maxHeapify(i){
  int l = 2*i;
  int r = 2*i+1;
  int valM;
  if(l <= size && heap[l] > heap[i]) valM = l;
  else valM = i;
  if(r <= size && heap[r] > heap[valM]) valM = r;
  if(valM != i){
    swap(&heap[i], &heap[valM]);
    maxHeapify(valM);
  }
}
 
void heapIncreaseKey(int i, int key){
  if(key < heap[i]) return;
  heap[i] = key;
  while(i>1 && heap[i/2]<heap[i]){
    swap(&heap[i], &heap[i/2]);
    i = i/2;
  }
}
 
void maxHeapInsert(int key){
  size++;
  heap[size] = -INF;
  heapIncreaseKey(size, key);
}
 
int heapExtractMax(){
  int valM;
  if(size < 1) return 0;
  valM = heap[1];
  heap[1] = heap[size--];
  maxHeapify(1);
  return valM;
}
 
main(){
  char input[20];
  size = 0;
  while(scanf("%s", input)){
    if(!strcmp(input, "end")) break;
    if(!strcmp(input, "extract")) printf("%d\n", heapExtractMax());
    else{
      char val[20];
      scanf("%s", val);
      maxHeapInsert(atoi(val));
    }
  }
  return 0;
}