Cpp 二叉树

#include<vector>
#include<iostream>
using namespace std;

//二叉树的一个节点结构
struct BinaryTreeNode {
    int val;
    BinaryTreeNode *left;
    BinaryTreeNode *right;
    BinaryTreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

//使用递归的方法创建二叉树
struct BinaryTreeNode *CreatBinaryTree(){
	int a;
	cin >> a; //有多少叶子就需要输入2倍个 0 才能结束创建进程
	if(a == 0) return NULL;

	struct BinaryTreeNode *newnode = (struct BinaryTreeNode*)malloc( sizeof(struct BinaryTreeNode) );
    newnode->val = a;
    newnode->left  = CreatBinaryTree();  //递归创建左子树
    newnode->right = CreatBinaryTree();  //递归创建右子树
    return newnode;
}

//先序遍历
void PreOrderTraverse(struct BinaryTreeNode *root){
	if(root){
		cout << root->val << ' ';
		PreOrderTraverse(root->left);
		PreOrderTraverse(root->right);
	}
}

//中序遍历
void InOrderTraverse(struct BinaryTreeNode *root){
	if(root){
		InOrderTraverse(root->left);
		cout << root->val << ' ';
		InOrderTraverse(root->right);
	}
}

//后序遍历
void LastOrderTraverse(struct BinaryTreeNode *root){
	if(root){
		LastOrderTraverse(root->left);
		LastOrderTraverse(root->right);
		cout << root->val << ' ';
	}
}

//层次遍历，使用队列，按照层级分别保存
void LevelOrderTraverse(BinaryTreeNode* root, int depth, vector<vector<int>> &result) {
    if(root==NULL) return;
    if(depth >= result.size()) result.push_back(vector<int>{});
    result[depth].push_back(root->val);
    LevelOrderTraverse(root->left,  depth + 1, result);
    LevelOrderTraverse(root->right, depth + 1, result);
}
void LevelOrderTraverse(BinaryTreeNode* root) {
    vector<vector<int>> result;
    LevelOrderTraverse(root, 0, result);
    for(auto line:result){
    	for(auto e:line) cout<<e<<' ';
    	cout<<endl;
	}
}

//二叉树节点总数目
int NodeNum(struct BinaryTreeNode *root){

	if(root)
		return 1+NodeNum(root->left)+NodeNum(root->right);
	else
		return 0;
}

//二叉树叶子节点数
int LeafNum(struct BinaryTreeNode *root){
	if(!root)
		return 0;
	else if( (root->left == NULL) && (root->right == NULL) )
		return 1;
	else
		return LeafNum(root->left) + LeafNum(root->right);
}

//二叉树最大深度
int maxDepth(struct BinaryTreeNode *root){
	if(root == NULL) return 0;
	return max(maxDepth(root->left), maxDepth(root->right)) + 1;
}

//二叉树最小深度(从根节点到最近叶子节点,注意是叶子)
int minDepth(struct BinaryTreeNode *root){
	if(root == NULL) return 0;
	if(root->left == NULL) return minDepth(root->right) + 1;
	if(root->right == NULL) return minDepth(root->left) + 1;
	return min(minDepth(root->left), minDepth(root->right)) + 1;
}

//二叉树所用路径
void binaryTreePaths(BinaryTreeNode* node,string path,vector<string> &result){
	path += to_string(node->val);
	//遍历到子节点了，
	if(node->left==NULL && node->right==NULL) result.push_back(path);
	if(node->left!=NULL) binaryTreePaths(node->left, path + "->",result);
	if(node->right!=NULL) binaryTreePaths(node->right,path + "->",result);
}
vector<string> binaryTreePaths(BinaryTreeNode* root) {
	vector<string> result;
	if(root!=NULL) binaryTreePaths(root,"",result);
	return result;
}

int main(){
	struct BinaryTreeNode *root;

	root = CreatBinaryTree();

	cout<<"二叉树总节点数为："<<NodeNum(root)<<endl;

	cout<<"二叉树叶子节点数为："<<LeafNum(root)<<endl;

	cout<<"二叉树最大深度(从根节点到最远叶子节点)："<<maxDepth(root)<<endl;

	cout<<"二叉树最小深度(从根节点到最近叶子节点)："<<minDepth(root)<<endl;

	cout<<"前序遍历结果:";
	PreOrderTraverse(root);
	cout<<endl;

	cout<<"中序遍历结果:";
	InOrderTraverse(root);
	cout<<endl;

	cout<<"后序遍历结果:";
	LastOrderTraverse(root);
	cout<<endl;

	cout<<"层次遍历结果:\n";
	LevelOrderTraverse(root);
	cout<<endl;

	cout<<"二叉树所有路径：\n";
	vector<string> allPaths = binaryTreePaths(root);
	for(auto e:allPaths) cout <<"\t" << e <<endl;

	return 0;
}
/*
测试用例：
3 9 0 0 20 15 0 0 7 0 0

3 9 15 0 0 7 0 0 20 0 0 

1 2 0 5 0 0 3 0 0
*/