c++二叉树文件读取

以下是C++中读取二叉树文件的示例代码：

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

struct TreeNode {
    char val;
    TreeNode* left;
    TreeNode* right;
    TreeNode(char x) : val(x), left(NULL), right(NULL) {}
};

void buildTree(TreeNode*& root, ifstream& fin) {
    char ch;
    if (!fin.eof()) {
        fin >> ch;
        if (ch == '0') {
            root = NULL;
        } else {
            root = new TreeNode(ch);
            buildTree(root->left, fin);
            buildTree(root->right, fin);
        }
    }
}

void preOrder(TreeNode* root) {
    if (root) {
        cout << root->val << " ";
        preOrder(root->left);
        preOrder(root->right);
    }
}

void inOrder(TreeNode* root) {
    if (root) {
        inOrder(root->left);
        cout << root->val << " ";
        inOrder(root->right);
    }
}

void postOrder(TreeNode* root) {
    if (root) {
        postOrder(root->left);
        postOrder(root->right);
        cout << root->val << " ";
    }
}

int main() {
    ifstream fin("tree.txt");
    TreeNode* root;
    buildTree(root, fin);
    cout << "Preorder traversal: ";
    preOrder(root);
    cout << endl;
    cout << "Inorder traversal: ";
    inOrder(root);
    cout << endl;
    cout << "Postorder traversal: ";
    postOrder(root);
    cout << endl;
    fin.close();
    return 0;
}