二叉树的中序遍历- 二叉树基本-递归

 

 

 

 

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

struct TreeNode {
    int val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};

// 创建二叉树
TreeNode* createBinaryTree() {
    TreeNode* root = new TreeNode(1);
    root->left = new TreeNode(2);
    root->right = new TreeNode(3);
    root->left->left = new TreeNode(4);
    root->left->right = new TreeNode(5);
    return root;
}

// 前序遍历
void preorder(TreeNode* root) {
    if (root == nullptr) return;
    cout << root->val << " ";
    preorder(root->left);
    preorder(root->right);
}

// 中序遍历
void inorder(TreeNode* root) {
    if (root == nullptr) return;
    inorder(root->left);
    cout << root->val << " ";
    inorder(root->right);
}

// 后序遍历
void postorder(TreeNode* root) {
    if (root == nullptr) return;
    postorder(root->left);
    postorder(root->right);
    cout << root->val << " ";
}

// 层次遍历
void levelOrder(TreeNode* root) {
    if (root == nullptr) return;
    
    queue<TreeNode*> q;
    q.push(root);
    
    while (!q.empty()) {
        TreeNode* current = q.front();
        q.pop();
        cout << current->val << " ";
        
        if (current->left != nullptr) q.push(current->left);
        if (current->right != nullptr) q.push(current->right);
    }
}

// 计算树高
int height(TreeNode* root) {
    if (root == nullptr) return 0;
    return max(height(root->left), height(root->right)) + 1;
}

// 计算节点数
int countNodes(TreeNode* root) {
    if (root == nullptr) return 0;
    return 1 + countNodes(root->left) + countNodes(root->right);
}

int main() {
    TreeNode* root = createBinaryTree();
    
    cout << "前序遍历: ";
    preorder(root);
    cout << endl;
    
    cout << "中序遍历: ";
    inorder(root);
    cout << endl;
    
    cout << "后序遍历: ";
    postorder(root);
    cout << endl;
    
    cout << "层次遍历: ";
    levelOrder(root);
    cout << endl;
    
    cout << "树高: " << height(root) << endl;
    cout << "节点数: " << countNodes(root) << endl;
    
    return 0;
}