C语言 数据结构 二叉树

Question

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#define max 50
typedef struct tree{
    struct tree *LChild;
    char data;
    struct tree *RChild;
}BitNode,*BiTree;
BiTree creatree(BiTree root,char*Data){
    static int flag=1;
    static int i = 0;
    if(Data[i]==' '){
        root = NULL;
        i++; 
        return 0;
    }
    if(flag!=1){root = (BitNode*)malloc(sizeof(BitNode));}
    root->data = Data[i];  
    //root->LChild = (BitNode*)malloc(sizeof(BitNode)); 
    //root->RChild = (BitNode*)malloc(sizeof(BitNode)); 
    i++;
    flag=0;
    creatree(root->LChild,Data);
    creatree(root->RChild,Data);
}

//先序遍历 
void PreOrder(BiTree root){
    if(root!=NULL){
        printf("%c",root->data);
        PreOrder(root->LChild);
        PreOrder(root->RChild); 
    }
}
//中序遍历
 void InOrder(BiTree root){
    if(root!=NULL){
        InOrder(root->LChild);
        printf("%c",root->data);
        InOrder(root->RChild); 
    }
}
//后序遍历
void PostOrder(BiTree root){
    if(root!=NULL){
        PostOrder(root->LChild);
        PostOrder(root->RChild);
        printf("%c",root->data); 
    }
} 
int main(){
    BiTree root;
    BiTree head;
    char *Data;
    Data=(char*)malloc(sizeof(char)*max);
    gets(Data);
    head =root = (BitNode*)malloc(sizeof(BitNode));
    creatree(root,Data);
    PreOrder(head);
    return 0;
} 

这代码有什么问题？

Answer 1

你的代码有几个问题。首先，你可能没有正确地初始化你的树结构，这可能导致内存泄漏或者错误的内存访问。其次，你在使用 gets() 函数，这在实际的编程环境中已经被废弃，因为它可能导致缓冲区溢出。

我会按照你的代码的逻辑进行修改，并给出详细的解释：

#include<stdio.h>  
#include<string.h>  
#include<stdlib.h>  
  
#define max 50  
  
typedef struct tree{  
    struct tree *LChild;  
    char data;  
    struct tree *RChild;  
}BitNode,*BiTree;  
  
BiTree creatree(BiTree root,char* Data, int* i){  
    static int flag=1;  
    if(Data[*i]==' '){  
        root = NULL;  
        (*i)++;   
        return root;  
    }  
    if(flag!=1){  
        root = (BitNode*)malloc(sizeof(BitNode));  
        flag = 0; // Set flag to 0 after malloc, to ensure it won't be allocated again for this node.  
    }  
    root->data = Data[*i];    
    root->LChild = creatree(root->LChild,Data, i);   
    root->RChild = creatree(root->RChild,Data, i);   
    (*i)++;  
    return root;  
}  
   
void PreOrder(BiTree root){  
    if(root!=NULL){  
        printf("%c",root->data);  
        PreOrder(root->LChild);  
        PreOrder(root->RChild);   
    }  
}  
  
void InOrder(BiTree root){  
    if(root!=NULL){  
        InOrder(root->LChild);  
        printf("%c",root->data);  
        InOrder(root->RChild);   
    }  
}  
  
void PostOrder(BiTree root){  
    if(root!=NULL){  
        PostOrder(root->LChild);  
        PostOrder(root->RChild);  
        printf("%c",root->data);   
    }  
}   
  
int main(){  
    BiTree root;  
    BiTree head;  
    char *Data;  
    int i = 0; // Initialize index.   
    Data=(char*)malloc(sizeof(char)*max);  
    // Remove gets() and replace with a safe method to get input. Here I use fgets().   
    if (fgets(Data, max, stdin) == NULL) {   
        printf("Invalid input.\n");   
        return -1;   
    }       
    head = root = (BitNode*)malloc(sizeof(BitNode));  // Allocate memory for the root.   
    root = creatree(root,Data, &i); // Pass the address of the index.   
    PreOrder(head);  // Print the tree in pre-order.   
    return 0;   
}