Question

I am able to print my expression tree in inorder. But I need to be able to print it in inorder with parenthesis. for example postorder 53+ should output (5+3)

I currently have:

void printTree(struct TreeNode *tree)
{
   if (tree != NULL)
    {
      if (isalpha(tree->info) || isdigit(tree->info))
        cout << "(";
      printTree( tree->left);
      cout<< tree->info;
      printTree(tree->right);
      if (isalpha(tree->info) || isdigit(tree->info))
        cout << ")";
    }
}

But this gives me incorrect output. If i enter postfix expression 62/5+ it gives me (6)/(2)+(5)

🙁

Answer 1

You need to distinguish between leaf nodes and non-leaf nodes. Only non-leaf nodes are enclosed in parantheses.

bool isLeaf(struct TreeNode* tree) {
    return tree->left == 0 && tree->right == 0;
}

void printTree(struct TreeNode* tree) {
    if (tree != NULL) { // this test could be omitted if the printed tree is not empty
        if (isLeaf(tree)) {
            cout << tree->info;
        }
        else {
            cout << "(";
            printTree(tree->left);
            cout << tree->info;
            printTree(tree->right);
            cout << ")";            
        }
    }
}