二叉树找最近祖先节点和到某一节点的路径

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
struct TreeNode{
	int val;
	struct TreeNode *left;
	struct TreeNode *right;
	TreeNode(int val) : val(val), left(nullptr), right(nullptr){}
};
//TreeNode* newNode(int val){
//	TreeNode* tmp = new TreeNode;
//	tmp->val = val;
//	tmp->left = nullptr;
//	tmp->right = nullptr;
//	return tmp;
//}
TreeNode* CreateTree(){
	TreeNode* p = nullptr;
	int val;
	cin >> val;
	if (val == 0)
		p = nullptr;
	else{
		p = new TreeNode(val);        //正确的使用方式  应该注意释放空间  delete和new对应存在
		p->left = CreateTree();
		p->right = CreateTree();
	}
	return p;
}
void PreOreder(TreeNode* root){
	if (root == nullptr)
		return;
	cout << root->val << ", ";
	PreOreder(root->left);
	PreOreder(root->right);
}
TreeNode* searchNode(TreeNode* root, int val){
	//临界条件
	if (root == nullptr)
		return nullptr;
	// 终止条件
	if (root->val == val){
		cout << "found" << endl;
		return root;
	}
	/*if (root->val != val && !root->left && !root->right)
		return nullptr;*/
	TreeNode*tmp_left = nullptr;
	TreeNode*tmp_right = nullptr;
	//框架  左子树 右子树
	if (root->left){
		tmp_left = searchNode(root->left, val);
	}
	if (root->right){
		tmp_right = searchNode(root->right, val);
	}
	//左右子树返回条件判断
	if (!tmp_left && !tmp_right) return nullptr;
	else if (!tmp_left || !tmp_right) return (!tmp_left) ? tmp_right : tmp_left;
}
/* root 根节点  val 查找的值 
	返回值：vector<vector<int> > ans
*/
void findPathToNode(TreeNode* root, int val, vector<int> &tmp, vector<vector<int> > &ans)
{
	/*犯错 ：刚开始使用的是vector<vector<int> > ans作为返回值，自己在函数内申请了ans，
	但是返回之后，里面没有任何的数据。这也是经常犯的错误，所以改成引用，直接传递到函数中去
	*/
	if (root == nullptr) return ;
	tmp.push_back(root->val);         //注意push的位置在 终止条件之前
	if (root->val == val){
		ans.push_back(tmp);
		//tmp.clear();       //当时还在这里犹豫 是不是要清空，实际上是不需要的 
	}
	//常用的框架
	if (root->left) findPathToNode(root->left, val, tmp, ans);
	if (root->right) findPathToNode(root->right, val, tmp, ans);
	tmp.pop_back();
}
/* 输入  vector<vector<int> > ans
	输出 祖先节点
*/
int findNearestNeighbor(vector<vector<int> > ans){
	//仅限于2条路径
	const unsigned int size = ans.size();
	 
	vector<int> v1 = ans.front(); 
	vector<int> v2 = ans.back();
	const unsigned int s1= v1.size();
	const unsigned int s2= v1.size();
	for (int i = 0; i < min(s1, s2); i++){
		int j = i + 1;
		if (v1[j] != v2[j]) return v1[i];
	}
	return -1;
	
}
int main()
{	
	/*使用的输入数据 7 3 2 0 0 5 0 0 10 0 11  5 0 0 0
						7
					3       10
				2       5       11
							  5
	*/

	vector<vector<int> > ans;
	vector<int> tmp;
	
	TreeNode* root;
	root = CreateTree();
	cout << "pre_order start###" << endl;
	PreOreder(root);
	cout << "pre_order end###" << endl;
	TreeNode* target = searchNode(root, 5);
	if (target){
		cout << "target->val " << target->val << endl;
	}
	else cout << "Sorry ,not found! " << endl;
	findPathToNode(root, 5, tmp, ans);
	cout << "result " << ans.size() << endl;
	for (auto item : ans){
		for (auto a : item){
			cout << a << "\t";
		}
		cout << endl;
	}
	cout << "find nearest neighbor" << endl;
	int num = findNearestNeighbor(ans);
	cout << num << endl;
	system("pause");
	return 0;
}