笔试的一道题目

前几天去了一家公司应聘,以为只有面试,没有前台mm给了我两页密密麻麻的笔试题.好久没有数据结构和算法方面的实践了,硬着头皮做了接近1个半小时,狼狈地交给了她,不过,幸好面试的时候发挥得还不错,否则这人就丢大了.

里面有一道题目是: 不用递归实现中序遍历一颗二叉树,当时一门心思在想利用goto语句能不能模拟递归的方法,越想越急,最后也没有写一个好的解答,回来后,趁着今天有空,写了一个实现,算是弥补一下缺憾,也算是再次熟悉一下数据结构和算法吧.

代码如下,有一部分是初始化和释放资源,显示二叉树用的,真正的遍历是MidDescendTree函数.

#include "stdafx.h" /*just used for win VC*/
#include "stdio.h"
#include "stdlib.h"
#include "string.h"

typedef struct tree{
        struct tree * left;
        struct tree * right;
        int data;
}TREE;

#define MAX_TREE_DEPTH 10
int InitTree(TREE **ppTree)
{
     int data;
     printf("Input the data of this node: ");
     scanf("%d",&data);
     if(data==-1)
     {
   *ppTree=0;
         return 0;
     }
     *ppTree = (TREE *)malloc(sizeof(TREE));
     if(*ppTree==NULL)
     {
         printf("Can not get enough mem!/n");
         return 1;
     }
     (*ppTree)->data = data;
     printf("Now, init the left child of node: %d /n",data);
     if(1==InitTree(&((*ppTree)->left)))
     {
         return 1;
     }
     printf("Now, init the right child of node: %d /n",data);
     return InitTree(&((*ppTree)->right));
}

void PrintTree(TREE *pTree,char * pPre)
{
 int len = strlen(pPre);
     if(pTree==NULL)
     {
         return;
     }
    
     printf("%d",pTree->data);
     printf("/n.%s",pPre);
     if(pTree->left)
     {
         PrintTree(pTree->left,strcat(pPre,".  "));
     }
  pPre[len]=0;/*经过多次递归，pPre会有累加*/
     printf("/n.%s",pPre);
     if(pTree->right)
     {
         PrintTree(pTree->right,strcat(pPre,".  "));
     }
   pPre[len]=0;
     return;
 }

void KillTree(TREE *pTree)
{
     if(pTree==NULL)
     {
         return;
     }
     KillTree(pTree->left);
     KillTree(pTree->right);
     free(pTree);
     return;    
 }
    

#define PUSH_NODE(node,dir) /
{/
 pHistory[lCurPos]=node;/
 lDirection[lCurPos++]=dir;/
}

#define POP_NODE(node,dir) /
{/
 if(lCurPos>0)/
 {/
  node = pHistory[--lCurPos];/
  dir = lDirection[lCurPos];/
  }/
  else/
 {/
  node = NULL;/
  }/
}

int MidDescendTree(TREE * pTree)
{
  TREE *pHistory[100] = {0};/*to record the history of descending*/
  int lDirection[100] = {0};/*0->none;1->left;2->right*/
  TREE *pCurNode = pTree;
  int lCurPos = 0;
  int lCurDir = 1;/*current Direction: Left first*/

  do
  {
   if(lCurDir==1)
   {
    if(pCurNode->left!=NULL)
    {
     PUSH_NODE(pCurNode,2);
     /*lCurDir must be 1,so donot need to set*/
     pCurNode = pCurNode->left;
     continue;
    }
   }
   if(lCurDir!=0)
   {
    printf("%2d  ",pCurNode->data);
   }
   if((pCurNode->right!=NULL)&&(lCurDir!=0))
   {
    PUSH_NODE(pCurNode,0);
    pCurNode = pCurNode->right;
    lCurDir=1;/*进入一个新的节点,从左边开始遍历*/
    continue;
   }
   POP_NODE(pCurNode,lCurDir); 
  }while(pCurNode);
 
  return 1;

}

int TestTree(void)
{
    int num;
    char chPre[2*MAX_TREE_DEPTH+1] = {' ',' ',0};
    TREE *pTree=NULL;
    InitTree(&pTree);
    PrintTree(pTree,chPre);
 printf("/n");

 MidDescendTree(pTree);

    KillTree(pTree);
    return 1;
}