A1151 LCA in a Binary Tree [先序中序建树找祖先]

对LCA递归的理解： （代码参考的大佬 理解这个花了蛮久 唉老蠢啦）
什么是什么的父节点就是搜索到这个结点的值等于u或者v就停下来
然后它是先往左边右边进行搜索，搜索到第一个结点的儿子节点相等的 就是最高的就停下来了，如果右边找不到 说明另一个还没找到的结点在左边已经找到的结点的更深处。

#include<iostream>
#include<vector>
#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<set>
#include<queue>
#include<unordered_map>
#include<cmath>
using namespace std;
const int maxn = 10010;
int m,n;
struct node
{
	int data;
	node* left, * right;
};
int in[maxn], pre[maxn];
node* buildtree(int prel, int prer, int inl, int inr)
{
	if (prel > prer)
		return NULL;
	node* root = new node;
	root->data = pre[prel];
	int i;
	for (i = inl; i <= inr; i++)
	{
		if (in[i] == pre[prel])
		{
			break;
		}
	}
	int leftnum = i - inl;
	root->left = buildtree(prel + 1, prel + leftnum, inl, i - 1);
	root->right = buildtree(prel + leftnum + 1, prer, i + 1, inr);
	return root;
}

bool findnode(int u)
{
	for (int i = 0; i < n; i++)
	{
		if (u == pre[i])
			return true;
	}
	return false;
}

node* LCA(node* root, int u, int v)
{
	if (root == NULL) return NULL;
	if (root->data == u || root->data == v) return root;
	node* left = LCA(root->left, u, v);
	node* right = LCA(root->right, u, v);  
	if (left && right) return root;
	return left == NULL ? right : left;
}

int main()
{
	cin >> m >> n; int u, v;
	for (int i = 0; i < n; i++)
	{
		cin >> in[i];
	}
	for (int i = 0; i < n; i++)
	{
		cin >> pre[i];
	}
	node* root = buildtree(0, n - 1, 0, n - 1);
	for (int i = 0; i < m; i++)
	{
		cin >> u >> v;
		if (findnode(u) == false && findnode(v) == false)
		{
			printf("ERROR: %d and %d are not found.
", u, v);
		}
		else if (findnode(u) == false || findnode(v) == false)
		{
			printf("ERROR: %d is not found.
", findnode(u) == false ? u : v);
		}
		else
		{
			node* temp = LCA(root, u, v);
			if (temp->data == u || temp->data == v) {
				printf("%d is an ancestor of %d.
", temp->data == u ? u : v, temp->data == u ? v : u);
			}
			else {
				printf("LCA of %d and %d is %d.
", u, v, temp->data);
			}
		}
	}

}