二叉树的建立与遍历

1 定义二叉树结构体

typedef struct BinaryTreeNode
{
    TelemType data;
    struct BinaryTreeNode *Left;
    struct BinaryTreeNode *Right;
}Node;

2 创建二叉树

Node* createBinaryTree()
{
    Node *p;
    TelemType ch;
    cin>>ch;
    if(ch == 0)     //如果到了叶子节点，接下来的左、右子树分别赋值为0
    {
        p = NULL;
    }
    else
    {
        p = (Node*)malloc(sizeof(Node));
        p->data = ch;
        p->Left  = createBinaryTree();  //递归创建左子树
        p->Right = createBinaryTree();  //递归创建右子树
    }
    return p;
}

PS：创建二叉树顺序为先中心节点，然后左子树，然后右子树，到了叶子节点后要把它的左右子树分别赋值为0。

3 遍历二叉树

3.1 先序遍历

void preOrderTraverse(Node* root)
{
    if( root )
    {
        cout<<root->data<<' ';
        preOrderTraverse(root->Left);
        preOrderTraverse(root->Right);
    }
}

3.2 中序遍历

void inOrderTraverse(Node* root)
{
    if( root )
    {
        inOrderTraverse(root->Left);
        cout<<root->data<<' ';
        inOrderTraverse(root->Right);
    }
}

3.3 后序遍历

void lastOrderTraverse(Node* root)
{
    if( root )
    {
        lastOrderTraverse(root->Left);
        lastOrderTraverse(root->Right);
        cout<<root->data<<' ';
    }
}

4 程序代码

#include <iostream>
#include<cstdio>
#include<cstdlib>
 
using namespace std;

typedef int TelemType;

typedef struct BinaryTreeNode
{
    TelemType data;
    struct BinaryTreeNode *Left;
    struct BinaryTreeNode *Right;
}Node;


//创建二叉树，顺序依次为中间节点->左子树->右子树
Node* createBinaryTree()
{
    Node *p;
    TelemType ch;
    cin>>ch;
    if(ch == 0)     //如果到了叶子节点，接下来的左、右子树分别赋值为0
    {
        p = NULL;
    }
    else
    {
        p = (Node*)malloc(sizeof(Node));
        p->data = ch;
        p->Left  = createBinaryTree();  //递归创建左子树
        p->Right = createBinaryTree();  //递归创建右子树
    }
    return p;
}

//先序遍历
void preOrderTraverse(Node* root)
{
    if( root )
    {
        cout<<root->data<<' ';
        preOrderTraverse(root->Left);
        preOrderTraverse(root->Right);
    }
}

//中序遍历
void inOrderTraverse(Node* root)
{
    if( root )
    {
        inOrderTraverse(root->Left);
        cout<<root->data<<' ';
        inOrderTraverse(root->Right);
    }
}

//后序遍历
void lastOrderTraverse(Node* root)
{
    if( root )
    {
        lastOrderTraverse(root->Left);
        lastOrderTraverse(root->Right);
        cout<<root->data<<' ';
    }
}


int main()
{
    Node *root = NULL;
    root = createBinaryTree();
    printf("\n二叉树建立成功！\n");
    cout<<endl;
 
    cout<<"前序遍历结果:"<<endl;
    preOrderTraverse(root);
    cout<<endl;
 
    cout<<"中序遍历结果:"<<endl;
    inOrderTraverse(root);
    cout<<endl;
 
    cout<<"后序遍历结果:"<<endl;
    lastOrderTraverse(root);
    cout<<endl;
 
    return 0;
}

5 程序运行结果