为什么会出现这样烦人的二叉搜索树 (bst) seg.fault 错误？

Question

input no. of elements , elements of binary search tree , input elemt whoose subtree you want to display

#include <stdio.h>

defn of struct node of bst

typedef struct node
{
int info;
struct node *right, *left;
}NODE;

insert fn , node at leaf

struct node* insertBst(struct node* root, int ele)
{

if(root == NULL)
{
    NODE* temp = (NODE*)malloc(sizeof(NODE));
    temp -> info = ele;
    temp -> right = temp -> left = NULL;
    return root;
}

else if(ele > root -> info)
{
    root -> right = insertBst(root -> right, ele);
}

else if(ele < root -> info)
{
    root -> left = insertBst(root -> left, ele);
}


}

searching for the address of the ele

NODE* search(int ele, NODE* root)
{
if( root == NULL) return NULL;
if(ele > root -> info)
{
    return search(ele, root -> right); 
}

else if( ele < root -> info)
{
    return search(ele, root -> left);
}

else if(ele == root -> info) //ele found
{
    return root;
}

 }

displaying the made bst using pre order : ROOT , LEFT, RIGHT

void preorder(NODE* root)
{
   if(root)
{
    printf("%d ", root -> info);
    preorder(root -> left);
    preorder(root -> right);
 }
}

driver where i call insert to create my bst, node whose subtree im >>displaying

int main()
{
int n, ele; //no. of elements in bst
NODE* root = NULL;
printf("no. of bst elements");
scanf("%d", &n);
printf("elements to be inserted in bst");
for(int i = 0; i < n; ++i)
{
    scanf("%d", &ele);
    NODE* t = insertBst(root, ele);
}

printf("element whose subtree needs to be displayed");
scanf("%d", ele); //elements whose subtree is to be diplayed
NODE *temp;
temp = search(ele, root);
preorder(temp);
}

Answer 1

段错误可能在行中：

scanf("%d", ele);

你应该传递 ele 的地址而不是它的值，就像你在 for 循环中所做的那样。

此外，您的程序将无法运行，因为函数 insertBst 永远不会分配根节点，因为任何时候 if(root == NULL) 为真（总是）您将分配一个节点，但您return 与 root 相同，但仍然是 NULL。你可能是想 return temp.

此外，在取消引用指针之前检查 temp（在 malloc 之后）是一个很好的做法，因为 malloc 可能会失败并且 return NULL，取消引用它会使你的程序崩溃。

为什么会出现这样烦人的二叉搜索树 (bst) seg.fault 错误？

why such an annoying binary search tree(bst) seg.fault error?

binary

tree

search

traversal

insert