BST迭代预遍历中的无限循环

Question

I am trying to iteratively traverse a BST in preorder, but this function is getting stuck in an infinite loop while printing. Could someone please tell me why this is happening?

1 typedef struct node_{
2     int data;
3     struct node_* left;
4     struct node_* right;
5 }BST; 

22 void preorder(BST* tree){
23     if(tree==NULL){
24         return;
25     }
26     // create stack 
27     stack* stack=create_stack();
28     // push data onto stack
29     push(stack,tree->data);
30     while(isEmpty(stack)==0){
31         struct node_ *node;
32         node->data=top(stack);
33         printf("%d ",node->data);
34         // pop value off stack
35         pop(stack);
36         if(node->right!=NULL){
37             //push right child onto stack
38             push(stack,node->right->data);
39         }
40         if(node->left!=NULL){
41             // push left child onto stack
42             push(stack,node->left->data);
43         }
44     }
45 }

Answer 1

Your loop never ends because node->right and node->left point to random memory locations. What is the value of node ? You haven't assigned anything to it. Its value is random.

Another problem is that you're pushing tree->data onto the stack. You actually want to push tree onto the stack. Then you can pop a node off the stack and assign it to node . Now you can print node->data and check the children of node .