以链表为储存结构创建二叉树的源代码

以下是使用链表储存结构创建二叉树的C++源代码：

#include <iostream>
using namespace std;

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

TreeNode* createBinaryTree() {
    int val;
    cin >> val;
    if (val == -1) {
        return nullptr;  // -1 代表叶节点的空节点
    }
    auto root = new TreeNode(val);
    root->left = createBinaryTree();
    root->right = createBinaryTree();
    return root;
}

void preOrder(TreeNode* root) {
    if (root == nullptr) {
        return;
    }
    cout << root->data << " ";
    preOrder(root->left);
    preOrder(root->right);
}

void inOrder(TreeNode* root) {
    if (root == nullptr) {
        return;
    }
    inOrder(root->left);
    cout << root->data << " ";
    inOrder(root->right);
}

void postOrder(TreeNode* root) {
    if (root == nullptr) {
        return;
    }
    postOrder(root->left);
    postOrder(root->right);
    cout << root->data << " ";
}

int main() {
    cout << "Please input the binary tree in pre-order sequence: ";
    auto root = createBinaryTree();
    cout << "The binary tree is created successfully!" << endl;

    cout << "The pre-order traversal of the binary tree is: ";
    preOrder(root);
    cout << endl;

    cout << "The in-order traversal of the binary tree is: ";
    inOrder(root);
    cout << endl;

    cout << "The post-order traversal of the binary tree is: ";
    postOrder(root);
    cout << endl;

    return 0;
}

运行结果如下：

Please input the binary tree in pre-order sequence: 1 2 -1 -1 3 4 -1 -1 5 -1 -1
The binary tree is created successfully!
The pre-order traversal of the binary tree is: 1 2 3 4 5 
The in-order traversal of the binary tree is: 2 1 4 3 5 
The post-order traversal of the binary tree is: 2 4 5 3 1 

在该程序中，我们首先使用前序遍历输入二叉树的节点值，其中 -1 代表叶节点的空节点。然后使用递归地方式创建二叉树，并返回根节点。最后分别使用前序、中序和后序遍历输出二叉树的节点值。