C++实现二叉树递归遍历

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

// 树结构
struct Tree {
public:
    string _data;
    Tree *lchild;
    Tree *rchild;
};

// 递归创建二叉树
void recursion_create_tree(Tree *tree) {
    string data;
    cin >> data;
    if (data == "a") {
        return;
    }
    Tree* _tree = new Tree;
    _tree -> _data = data;
    tree = _tree;
    recursion_create_tree(tree -> lchild);
    recursion_create_tree(tree -> rchild);
}

// 前序遍历：根节点->左子树->右子树
void pre_traverse(Tree *tree) {
    if (tree) {
        cout << tree -> _data << endl;;
        if (tree -> lchild) {
            pre_traverse(tree -> lchild);
        }
        if (tree -> rchild) {
            pre_traverse(tree -> rchild);
        }
    }
}

// 中序遍历：左子树->根节点->右子树
void in_traverse(Tree *tree) {
   if (tree) {
       if (tree -> lchild) {
           in_traverse(tree -> lchild);
       }
       cout << tree -> _data << endl;
       if (tree -> rchild) {
           in_traverse(tree -> rchild);
       }
   }
}

// 后序遍历：左子树->右子树->根节点
void beh_traverse(Tree *tree) {
    if (tree) {
        if (tree -> lchild) {
            beh_traverse(tree -> lchild);
        }
        if (tree -> rchild) {
            beh_traverse(tree -> rchild);
        }
        cout << tree -> _data << endl;
    }
}

int main(int argc, char** args) {
    Tree* tree;
    recursion_create_tree(tree);
    pre_traverse(tree);
    in_traverse(tree);
    beh_traverse(tree);
    return 0;
}