二叉树

引自

#include<iostream>
using namespace std;

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

//按照前序顺序建立二叉树
void createBiTree(TreeNode* &T) {    //目的是让传递进来的指针发生改变        
    char c;
    cin >> c;
    if('#' == c)         //当遇到#时，令树的根节点为NULL，从而结束该分支的递归
        T = NULL;
    else
    {
        T = new TreeNode(c);
        createBiTree(T->left);
        createBiTree(T->right);
    }
}

//前序遍历二叉树并打印
void preTraverse(TreeNode* T)
{
    if(T)
    {
        cout<<T->val<<" ";
        preTraverse(T->left);
        preTraverse(T->right);
    }
}
//中序遍历二叉树并打印
void midTraverse(TreeNode* T)
{
    if(T)
    {
        midTraverse(T->left);
        cout<<T->val<<" ";
        midTraverse(T->right);
    }
}
//后续遍历二叉树并打印
void postTraverse(TreeNode* T)
{
    if(T)
    {
        postTraverse(T->left);
        postTraverse(T->right);
        cout<<T->val<<" ";
    }
}
int main()
{
    TreeNode *T;                //声明一个指向二叉树根节点的指针               
    createBiTree(T);
    cout<<"二叉树创建完成！"<<endl;
    cout<<"前序遍历二叉树："<<endl;
    preTraverse(T);
    cout<<endl;
    cout<<"中序遍历二叉树："<<endl;
    midTraverse(T);
    cout<<endl;
    cout<<"后序遍历二叉树："<<endl;
    postTraverse(T);
    return 0;
}