在判断是否符合堆的特性时，我一开始使用的判断语句是：

if ((heap[root] > heap[2 * root] || heap[root] > heap[2 * root + 1])
 && (heap[2 * root]!= -999999 && heap[2 * root + 1]!= -999999))
		flag_min = 0;//不是小根堆；

虽然我将每个空节点都设置为了-999999.但是这样有一个致命的错误，就是root*2可能超过设置的数组长度。导致错误。
后来改为了：

if (2 * root <= N && heap[root] > heap[2 * root]) flag_min = 0;
if (2 * root + 1 <= N && heap[root] > heap[2 * root + 1]) flag_min = 0;

这样可以直接防止数据越界。

#include<bits/stdc++.h>
using namespace std;
vector<int> heap(1009),ans;
int flag_min, flag_max;
int M, N;
void preTraversal(int root) {
	if (root > N) return;
	preTraversal(root * 2);
	preTraversal(root * 2 + 1);
	ans.push_back(heap[root]);
}
void judge_maxheap(int root) {
	if (root > N) return;
	//出错的地方
	//----------------------------------------------------------------------//
	if (2 * root <= N && heap[root] < heap[2 * root]) flag_max = 0;
	if (2 * root + 1 <= N && heap[root] < heap[2 * root + 1]) flag_max = 0;
	//----------------------------------------------------------------------//
	judge_maxheap(root * 2);
	judge_maxheap(root * 2 + 1);
}
void judge_minheap(int root) {
	if (root > N) return;
	//----------------------------------------------------------------------//
	if (2 * root <= N && heap[root] > heap[2 * root]) flag_min = 0;
	if (2 * root + 1 <= N && heap[root] > heap[2 * root + 1]) flag_min = 0;
	//----------------------------------------------------------------------//
	judge_minheap(root * 2);
	judge_minheap(root * 2 + 1);
}
int judge() {
	if (heap[1] > heap[2]) {//当大根堆判断
		flag_min = 0;
		judge_maxheap(1);
		if(flag_max == 1)
			return 1;
	}
	else if (heap[1] < heap[2]) {//当小根堆判断
		flag_max = 0;
		judge_minheap(1);
		if(flag_min == 1)
			return 1;
	}
	else {
		judge_minheap(1); judge_maxheap(1);
		if (flag_max + flag_min == 1) return 1;
	}
	return 0;
}
int main() {
#ifdef ONLINE_JUDGE
#else
	freopen("Text.txt", "r", stdin);
#endif // ONLINE_JUDGE

	cin >> M >> N;
	for (int j = 0; j < M; j++) {
		flag_min = 1; flag_max = 1;
		fill(heap.begin(), heap.end(), -999999);
		for (int i = 1; i <= N; i++) {
			cin >> heap[i];
		}
		if (judge() == 1) {
			if (flag_max == 1) cout << "Max Heap" << endl;
			else cout << "Min Heap" << endl;
		}
		else {
			cout << "Not Heap" << endl;
		}
		preTraversal(1);
		cout << ans[0];
		for (int i = 1; i < N; i++)
			cout << " " << ans[i];
		cout << endl;
		ans.clear();
	}
}