C语言遍历二叉树的时候，出现了读取访问权限的问题，要怎么解

Question

问题遇到的现象和发生背景

C语言遍历二叉树的时候，出现了读取访问权限的问题，要怎么解

#include <stdio.h>
#include <malloc.h>


#define MaxLength 100                            
#define MaxSize 50                                


typedef char ElemType;                             

typedef struct BTNode                            
{
    ElemType data;                                    
    struct BTNode* lchild;                            
    struct BTNode* rchild;                            
}BTreeNode;

typedef struct                                    
{
    BTreeNode* node[MaxSize];                         
    int top;
}SqStack;


void StackInit(SqStack** s)                        
{
    (*s) = (SqStack*)malloc(sizeof(SqStack));
    (*s)->top = -1;
}

void StackDestroy(SqStack** s)                 
{
    free(*s);
}

void BTreeInit(BTreeNode** b)                    
{
    (*b) = (BTreeNode*)malloc(sizeof(BTreeNode));
    (*b)->lchild = NULL;                                
    (*b)->rchild = NULL;
}

void BTreeCreat(BTreeNode** b)                    
{
    BTreeNode* t;                                    
    ElemType e;                                        
    ElemType elems[MaxLength];                        
    SqStack* s;                                    
    int k;                                        
    int i;                                        

    t = NULL;
    i = 0;

    StackInit(&s);                                

    printf("elems input:");
    gets_s(elems,100);                                     
    e = elems[i];                                    

    while (e != '\0')
    {
        switch (e)
        {
        case '(':
            s->top++;
            s->node[s->top] = t;                    
            k = 1;                                
            break;
        case ')':
            s->top--;                        
            break;
        case ',':
            k = 2;                            
            break;
        default:
            BTreeInit(&t);                        
            t->data = e;                            
            if (i == 0)                        
            {
                (*b) = t;                            
            }
            else
            {
                switch (k)
                {
                case 1:                        
                    s->node[s->top]->lchild = t;
                    break;
                case 2:                        
                    s->node[s->top]->rchild = t;
                    break;
                }
            }
        }
        i++;
        e = elems[i];                                    
    }

    StackDestroy(&s);
}

void PreOrderTraverse(BTreeNode* b){
    if (b == NULL)
        return;
    printf("%c ",  b->data);
    PreOrderTraverse(b->lchild);
    PreOrderTraverse(b->rchild);
}
void InOrderTraverse(BTreeNode* b)
{
    if (b == NULL)
        return;
    InOrderTraverse(b->lchild);
    printf("%c ", b->data);
    InOrderTraverse(b->rchild);
}
void PostOrderTraverse(BTreeNode* b)
{
    if (b == NULL)
        return;
    PostOrderTraverse(b->lchild);
    PostOrderTraverse(b->rchild);
    printf("%c ", b->data);
}




void BTreeDestroy(BTreeNode** b)                
{
    free(*b);
}


int main()
{
    BTreeNode* b;

    BTreeInit(&b);

    BTreeCreat(&b);                            
    PostOrderTraverse(&b);
    printf("\n");

    BTreeDestroy(&b);

    return 0;
}

运行结果及报错内容

Answer 1

注意二叉树的链式结构要先调用 malloc 分配子节点内存，才能使子节点不为null，这时我们就可以赋值了