Binary tree traversal Inorder output is wrong why? - linked-list

Question

Can someone explain why my output is wrong and how to fix it?
for example: i will input A B C D E
output is giving me A B C D E
insead of Inorder Traversal: D B E A C
this is my code:
int main()
{
struct node *root = NULL;
int choice, n; // item
char item;
do
{
printf("\n1. Insert Node");
printf("\n2. Traverse in Inorder");
printf("\nEnter Choice : ");
scanf("%d",&choice);
switch(choice)
{
case 1:
root = NULL;
printf("\n\n Nodes : ");
scanf("%d",&n);
for(int i = 1; i <= n; i++)
{
printf("\nEnter data for node %d : ", i);
scanf(" %c",&item);
root = Create(root,item);
}
break;
case 2:
printf("\nBST Traversal in INORDER \n");
Inorder(root); break;
default:
printf("\n\nINVALID OPTION TRY AGAIN\n\n"); break;
}
} while(choice != 3);
}
struct node *Create(struct node *root, char item)
{
if(root == NULL)
{
root = (struct node *)malloc(sizeof(struct node));
root->left = root->right = NULL;
root->data = item;
return root;
}
else
{
if(item < root->data )
root->left = Create(root->left,item);
else if(item > root->data )
root->right = Create(root->right,item);
else
printf(" Duplicate Element !! Not Allowed !!!");
return(root);
}
}
void Inorder(struct node *root)
{
if( root != NULL)
{
Inorder(root->left);
printf(" %c ",root->data);
Inorder(root->right);
}
}
i doubled check the algorithm of The traversal Inorder but my output is still wrong i don't understand why? did i miss something here

Answer 1

The result is as expected. The in-order traversal should not produce D B E A C for your input of A B C D E
This is how the tree is constructed.
First the root is created with value A
Then B is inserted. As B > A, it is inserted as a right child of the root:
A
\
B
Then B is inserted. As C > A, it is inserted in the right subtree. There again we find C > B, so the new node will be inserted as a right child of B:
A
\
B
\
C
In the same way D and then E are inserted, giving this tree:
A
\
B
\
C
\
D
\
E
Note that this tree is not balanced at all. That's what happens when you insert nodes in their lexical order. If you would insert them in a more random order, we would expect the tree to be more balanced.
But it does not actually matter for the in-order traversal. What you have implemented is a binary search tree (BST). And one important property of BSTs is that their in-order traversal always produces the data in their right order. And so irrespective of the order in which you input the letters A B C D and E, the in-order traversal should always output this sequence:
A B C D E
This is correct.