I am trying to implement the BST in iterative method using c programming, inserting only one element will not cause segmentation error(2nd line in main function root = insert(root,50). but adding more than one element in BST shows segmentation error. i don't know where the mistake. The code is as follows

#include <stdio.h>
#include <stdlib.h>

struct bstnode
{
    int data;
    struct bstnode *left;
    struct bstnode *right;
};



struct bstnode* getnode(int data)
{
   
    struct bstnode *temp = malloc(sizeof(struct bstnode));
    if(temp == NULL)
    {
        printf("failed");
    }
    temp->data = data;
    temp->left = temp->right = NULL;
    return temp;
}

struct bstnode* insert(struct bstnode *root,int data)
{
    if(root == NULL)
    {
        root = getnode(data);
        return root;
    }
     
    struct bstnode *temp = root;
    struct bstnode *parent;
    int flag;
    while(temp != NULL)
    {
       parent = temp; 
       if(data < temp->data)
       {
           temp = temp->left;
           flag = 1;
       }
       if(data > temp->data)
       {
           temp = temp->right;
           flag = 0;
       }
    }
    
    if(flag == 1)
    {
        parent->left = getnode(data);
    }
    else
        parent->right = getnode(data);
     
     return root; 
    
}

void inorder(struct bstnode* root)
{
    if (root != NULL) {
        inorder(root->left);
        printf("%d \n", root->data);
        inorder(root->right);
    }
}

int main() {
    struct bstnode *root = NULL;
    root = insert(root, 50);
    insert(root, 30);
    insert(root, 20);
    insert(root, 40);
    insert(root, 70);
    insert(root, 60);
    insert(root, 80);
    
    inorder(root);
    
    return 0;
}

CodePudding user response：

Think what happens here when data is less than temp->data and temp->left is NULL?

   if(data < temp->data)
   {
       temp = temp->left;
       flag = 1;
   }
   if(data > temp->data)
   {
       temp = temp->right;
       flag = 0;
   }

You probably want to do an else if instead of just if in this case.

Also what happens if data is equal to temp->data?