学步园

#include "stdio.h"
#include "malloc.h"

struct Node* current = NULL; //声明的一个全局变量表示的是链表的尾部

//二叉树
struct Node
{
int value;
struct Node* left;  //左儿子节点
struct Node* right; //右儿子节点
};

void addLeftNode(struct Node *node, struct Node *left) //添加一个左儿子
{
node->left = left;
}

void addRightNode(struct Node *node, struct Node *right) //添加一个右儿子
{
node->right = right;
}

struct Node* createNode(int value)
{
struct Node* node = (struct Node*)malloc(sizeof(struct Node));
node->value = value;
node->left = NULL;
node->right = NULL;
return node;
}

void firstRoot(struct Node* root) //递归先根遍历
{
printf("%d\n", root->value);

if(root->left != NULL)
firstRoot(root->left);

if(root->right != NULL)
firstRoot(root->right);
}

void middleRoot(struct Node* root) //递归中根遍历
{
if(root->left != NULL)
middleRoot(root->left);

printf("%d\n", root->value);

if(root->right != NULL)
middleRoot(root->right);
}

void lastRoot(struct Node* root) //递归后根遍历
{
if(root->left != NULL)
lastRoot(root->left);

if(root->right != NULL)
lastRoot(root->right);

printf("%d\n", root->value);

}

/*
1
-
   2  3  生成树的形状
   -  -
  4 5 6 7
*/

int main()
{

struct Node* first = createNode(1);
addLeftNode(first, createNode(2));
addRightNode(first, createNode(3));

addLeftNode(first->left, createNode(4));
addRightNode(first->left, createNode(5));

addLeftNode(first->right, createNode(6));
addRightNode(first->right, createNode(7));

firstRoot(first);
middleRoot(first);
lastRoot(first);
getchar();
return 0;
}