二叉树遍历的递归算法

二叉树遍历

递归算法

• BinaryTree.h

//
// Created by Administrator on 2021/10/25.
//

#ifndef TEST_BINARYTREE_H
#define TEST_BINARYTREE_H

#include <iostream>

using namespace std;

typedef char ElemType;

typedef struct BiNode {
    ElemType data;
    BiNode *left;
    BiNode *right;

    BiNode(ElemType val) {
        data = val;
        left = nullptr;
        right = nullptr;
    }
} BiNode, *BiTree;

class BinaryTree {
public:
    void Create();

    int getSize();

    int getHeight();

    void preOrder();

    void inOrder();

    void postOrder();

    void destroy();

private:
    BiTree create();

    void preOrder(BiTree root);

    void inOrder(BiTree root);

    void postOrder(BiTree root);

    void destroy(BiTree root);

    int getHeight(BiTree root);

    void AddNode(ElemType key, int direction, BiTree root);

    BiTree m_root;
    int size;
};

#endif //TEST_BINARYTREE_H

• BinaryTree.cpp

//
// Created by Administrator on 2021/10/25.
//

#include "BinaryTree.h"

void BinaryTree::Create() {
    size = 0;
    m_root = create();
}

int BinaryTree::getSize() {
    return size;
}

int BinaryTree::getHeight() {
    return getHeight(m_root);
}

void BinaryTree::preOrder() {
    cout << "先序遍历：" << endl;
    preOrder(m_root);
    cout << endl;
}

void BinaryTree::inOrder() {
    cout << "中序遍历：" << endl;
    inOrder(m_root);
    cout << endl;
}

void BinaryTree::postOrder() {
    cout << "后序遍历：" << endl;
    postOrder(m_root);
    cout << endl;
}

void BinaryTree::destroy() {
    destroy(m_root);
}


BiTree BinaryTree::create() {
    BiTree current = nullptr;
    ElemType val;
    // 输入值
    cin >> val;
    if (val == '#') {
        // 当前子树为空
        return nullptr;
    } else {
        // 递归创建左右子树
        size++;
        current = new BiNode(val);
        current->left = create();
        current->right = create();
        return current;
    }
}

void BinaryTree::preOrder(BiTree root) {
    if (root == nullptr)
        return;
    else {
        cout << root->data << " --> ";  // 先打印根节点
        preOrder(root->left);           // 遍历左子树
        preOrder(root->right);          // 遍历右子树
    }
}

void BinaryTree::inOrder(BiTree root) {
    if (root == nullptr)
        return;
    else {
        inOrder(root->left);
        cout << root->data << " --> ";
        inOrder(root->right);
    }
}

void BinaryTree::postOrder(BiTree root) {
    if (root == nullptr)
        return;
    else {
        postOrder(root->left);
        postOrder(root->right);
        cout << root->data << " --> ";
    }
}

void BinaryTree::destroy(BiTree root) {
    if (root) {
        destroy(root->left);
        destroy(root->right);
        // 释放节点
        delete root;
        root = nullptr;
        size = 0;
    }
}

/**
 *
 * @param root
 * @return 递归得到树高
 */
int BinaryTree::getHeight(BiTree root) {
    if (root == nullptr)
        return 0;
    int left_height = getHeight(root->left);
    int right_height = getHeight(root->right);
    return (left_height > right_height) ? (left_height + 1) : (right_height + 1);
}

/**
 * 前序遍历的方式创建
 * @param key 值
 * @param direction 0是从左子树插入，1是从右子树插入
 * @param root 被插入的根节点
 */
void BinaryTree::AddNode(const ElemType key, int direction, BiTree root) {
    if (direction == 0) {
        // 插入到左子树
        if (root->left == nullptr)
            root->left = new BiNode(key);
        else
            AddNode(key, direction, root->left);
    } else if (direction == 1) {
        // 插入到右子树
        if (root->right == nullptr)
            root->right = new BiNode(key);
        else
            AddNode(key, direction, root->right);
    }
}

• main.cpp

#include <iostream>
#include "BinaryTree.h"

using namespace std;

int main() {

    BinaryTree tree{};
    cout << "按先序遍历方式创建树：" << endl;
    // ABCD##E##FG###HI#J##K##
    tree.Create();
    cout << "树的高度为：" << tree.getHeight() << endl;
    cout << "树的节点为：" << tree.getSize() << endl;
    tree.preOrder();
    tree.inOrder();
    tree.postOrder();
    tree.destroy();

    return 0;
}

• 截图