二叉堆

int heap[MAX], sz = 0;
void push(int x) {
  int i = sz++;
  while (i > 0) {
    int p = (i - 1) / 2;
    if (heap[p] <= x) break;
    heap[i] = heap[p];
    i = p;
  }
  heap[i] = x;
}
int pop() {
  int ret = heap[0];
  int i = 0;
  int x = heap[--sz];
  while(i * 2 + 1 < sz) {
    int a = 2 * i + 1;
    int b = 2 * i + 2;
    if (b < sz && heap[b] < heap[a]) {
      a = b;
    }
    if (heap[a] >= a) break;
    heap[i] = heap[a];
    i = a;
  }
  heap[i] = x;
  return ret;
}