240516 최소 힙

private static int[] heap = new int[100001];
private static int heapsize = 0;

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	int n = Integer.parseInt(br.readLine());
	StringBuilder sb = new StringBuilder();

	for (int i = 0; i < n; i++) {
		int num = Integer.parseInt(br.readLine());
		if (num != 0) {
			offer(num);
		} else {
			sb.append(poll()).append("\n");
		}
	}
	System.out.print(sb);
}

public static void offer(int item) {
	heap[++heapsize] = item;
	for (int i = heapsize; i > 1; i /= 2) {
		if (heap[i] < heap[i / 2]) {
			swap(i, i / 2);
		} else {
			break;
		}
	}
}

public static int poll() {
	if (heapsize == 0)
		return 0;
	int pollData = heap[1];
	heap[1] = heap[heapsize--];

	int parent = 1;
	int leftChild;
	int rightChild;

	while (parent * 2 <= heapsize) {
		leftChild = parent * 2;
		rightChild = leftChild + 1;

		int minChild = (rightChild <= heapsize && heap[rightChild] < heap[leftChild]) ? rightChild : leftChild;

		if (heap[parent] <= heap[minChild])
			break;

		swap(parent, minChild);
		parent = minChild;
	}
	return pollData;
}

public static void swap(int a, int b) {
	int temp = heap[a];
	heap[a] = heap[b];
	heap[b] = temp;
}

출처:https://www.acmicpc.net/problem/1927