C Primer+Plus（十七）高级数据表示 编程练习(二）

7、编写一个程序，能打开、读入一个文本文件并统计文件中每个单词出现的次数。用改进的二叉搜索树存储单词及其出现的次数。程序读入文件后，会提供一个有三个选项的菜单。第一个选项为列出所有单词连同其出现的次数。第二个选项为让您输入一个单词，程序报告该单词在文件中出现的次数。第三个选项为退出。

断断续续编写代码、测试，花了差不多两天时间，总算告成。

*建立该问题的二叉树节点模型

//BST Model--START------------------
typedef struct node
{char word[15];int times;        //出现的次数struct node *left;struct node *right;
}Node;typedef struct tree
{Node *root;int num;      //树中单词数
}Tree;
//BST Model--FINISH--------------------

*研究本题需求，实现接口代码

//BST function START-----------------------------
//初始化树
void IniTree(Tree *ptree)
{ptree->root=NULL;ptree->num=0;
}//查找树中有无指定单词
//若未找到，返回NULL；若找到返回指定项目所在节点地址
Node *FindWord(char word[15],const Node *root)
{Node *pnode;pnode=root;if(root==NULL){return NULL;}while(strcmp(word,pnode->word)!=0 && (pnode!=NULL)){  if(strcmp(word,pnode->word)<0)pnode=pnode->left;elsepnode=pnode->right;}return pnode;
}//添加单词节点
//通过FindWord做支撑，若存在，则相应节点次数+1
//若不存在，则找到合适的空位，同时定位该空位的父节点
//创建该单词的节点，并判断在空位父节点的左还是右，然后添加
void AddWord(char word[15],Tree *ptree)
{Node *pnode,*newnode,*fathernode;pnode=FindWord(word,ptree->root);if(pnode!=NULL){     pnode->times++;}else{newnode=ptree->root;while(newnode!=NULL)     //找空位，并且定位空位的父节点
     {if(strcmp(word,newnode->word)<0){fathernode=newnode;      newnode=newnode->left;}else{fathernode=newnode;      newnode=newnode->right;}} newnode=(Node*)malloc(sizeof(Node));newnode->left=NULL;newnode->right=NULL;newnode->times=1;strcpy(newnode->word,word);   //设置节点信息if(ptree->root==NULL)  //如果树为空
  {ptree->root=newnode;ptree->num++; }else{if(strcmp(word,fathernode->word)<0)   //说明父节点左子节点为空
       {    fathernode->left=newnode;ptree->num++;}else{    fathernode->right=newnode;ptree->num++;}}}
}//打印树中单词信息
void PrintTree(const Node *root)
{if(root!=NULL){  PrintTree(root->left);printf("the word is %s,its times is %d.\n",root->word,root->times);PrintTree(root->right);}
}//输入单词，显示次数
void showtimes(const Tree *ptree)
{Node *pnode;char word[15];printf("input the word.\n");gets(word);pnode=FindWord(word,ptree->root);if(pnode==NULL)printf("the word:%s is not in the tree.\n",word);elseprintf("the word:%s times in tree is:%d.\n",word,pnode->times);}
//BST function FINISH---------------

 

*完整代码：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>//BST Model--START------------------
typedef struct node
{char word[15];int times;        
struct node *left;struct node *right;
}Node;typedef struct tree
{Node *root;int num;      
}Tree;
//BST Model--FINISH--------------------//BST function START-----------------------------
//初始化树
void IniTree(Tree *ptree)
{ptree->root=NULL;ptree->num=0;
}//查找树中有无指定单词
Node *FindWord(char word[15],const Node *root)
{Node *pnode;pnode=root;if(root==NULL){return NULL;}while(strcmp(word,pnode->word)!=0 && (pnode!=NULL)){  if(strcmp(word,pnode->word)<0)pnode=pnode->left;elsepnode=pnode->right;}return pnode;
}//添加单词节点
void AddWord(char word[15],Tree *ptree)
{Node *pnode,*newnode,*fathernode;pnode=FindWord(word,ptree->root);if(pnode!=NULL){     pnode->times++;}else{newnode=ptree->root;while(newnode!=NULL)     
      {if(strcmp(word,newnode->word)<0){fathernode=newnode;      newnode=newnode->left;}else{fathernode=newnode;      newnode=newnode->right;}} newnode=(Node*)malloc(sizeof(Node));newnode->left=NULL;newnode->right=NULL;newnode->times=1;strcpy(newnode->word,word);   
if(ptree->root==NULL)  
      {ptree->root=newnode;ptree->num++; }else{if(strcmp(word,fathernode->word)<0)   
          {    fathernode->left=newnode;ptree->num++;}else{    fathernode->right=newnode;ptree->num++;}}}
}//打印树中单词信息
void PrintTree(const Node *root)
{if(root!=NULL){  PrintTree(root->left);printf("the word is %s,its times is %d.\n",root->word,root->times);PrintTree(root->right);}
}//输入单词，显示次数
void showtimes(const Tree *ptree)
{Node *pnode;char word[15];printf("input the word.\n");gets(word);pnode=FindWord(word,ptree->root);if(pnode==NULL)printf("the word:%s is not in the tree.\n",word);elseprintf("the word:%s times in tree is:%d.\n",word,pnode->times);}
//BST function FINISH---------------int main()
{FILE *fp;Tree *wordtree;Node *new_node;char newword[15];char ch,cc;int i=0;
//读入文件，创建单词的二叉搜索树-----------------------fp=fopen("ab.txt","r");if(fp==NULL){fprintf(stdout,"can't open the file.\n");getch();exit(1);}
//初始化树
  IniTree(wordtree);//读入文件字符while((ch=getc(fp))!=EOF){if((ch>='a'&&ch<='z')||(ch>='A'&&ch<='Z')){newword[i]=ch;i++;}else{if(i==0)             
continue;else                 
        {newword[i]='\0';AddWord(newword,wordtree);  //加入单词树i=0;}}}
//针对文本最后字符为字母，则还未设置字符串结束符就跳出while循环了
//增加本段代码处理if(i!=0){newword[i]='\0';AddWord(newword,wordtree);  //加入单词树
   }  //单词二叉搜索树创建完成---------------------------------------------------------    
printf("-----Please choose--------\n");printf("a:---show all words-------\n");printf("b:---some word------------\n");printf("c:---Quit-----------------\n");while((cc=getch())!='c'){switch(cc){case 'a':PrintTree(wordtree->root);break;case 'b':showtimes(wordtree);break;}printf("-----Please choose--------\n");printf("a:---show all words-------\n");printf("b:---some word------------\n");printf("c:---Quit-----------------\n");}fclose(fp);return 0;
}