二叉树中序遍历 (C语言实现)

在计算机科学中，树是一种重要的非线性数据结构，直观地看，它是数据元素（在树中称为结点）按分支关系组织起来的结构。二叉树是每个节点最多有两个子树的有序树。通常子树被称作“左子树”（left subtree）和“右子树”（right subtree）。二叉树常被用于实现二叉查找树和二叉堆。

如下是实现创建二叉树和二叉树中序遍历的代码：

 #include <stdio.h>
 #include <stdlib.h>
 #include <memory.h>

 typedef struct _tree_node{
     char data;
     struct _tree_node * left;
     struct _tree_node * right;
     struct _tree_node * father;
 }tree_node;

 void createTree(tree_node * root);
 void inorderTraverseTree(tree_node * pRoot);

 int main()
 {
     tree_node root;
     memset(&root,  , sizeof(tree_node));
     printf("Please create the tree: \n");
     createTree(&root);
     printf("The inorder traverse result is: \n");
     inorderTraverseTree(&root);
     return ;
 }

 //inorder traversal
 void inorderTraverseTree(tree_node * pRoot)
 {
     tree_node * pCur = pRoot;
     if(pCur != NULL)
     {
         if(pCur->left != NULL)
         {
             inorderTraverseTree(pCur->left);
         }
         else
         {
             printf("%c ", pCur->data);
             return;
         }
         printf("%c ", pCur->data);

         if(pCur->right != NULL)
         {
             inorderTraverseTree(pCur->right);
         }
     }
 }

 //Create the binary tree
 void createTree(tree_node * pRoot)
 {
     char ch = ;
     tree_node * pCur = pRoot;
     while((ch = getchar())!= 'e')
     {
         //printf("%c" , ch);
         tree_node * pNewNode = (tree_node *)malloc(sizeof(tree_node));
         pNewNode->left = NULL;
         pNewNode->right = NULL;
         pNewNode->father = NULL;
         if(ch == 'L')
         {
             //printf("Input L\n");
             pNewNode->data = getchar();
             pNewNode->father = pCur;
             pCur->left = pNewNode;
             pCur = pNewNode;
         }
         else if(ch == 'R')
         {
             //printf("Input R\n");
             pNewNode->data = getchar();
             pNewNode->father = pCur;
             pCur->right = pNewNode;
             pCur = pNewNode;
         }
         else if(ch == 'B')
         {
             //printf("Input B\n");
             free(pNewNode);
             if(pCur->father != NULL)
                 pCur = pCur->father;
             else
                 printf("It's the top\n");
         }
     }
 }

构造这样一颗二叉树：

程序运行结果为：