Preorder Traversal

Preorder Traversal

Preorder: current node → left subtree → right subtree

        4
       / \
      2   6
     / \ / \
    1  3 5  7

Preorder visits: 4 2 1 3 6 5 7

Notice: the root comes first. Preorder is useful for copying a tree — if you insert nodes into a new tree in preorder, you get the same structure. It is also used in expression trees where operators precede their operands.

Implementation

void preorder(struct Node *root) {
    if (root == NULL) return;
    printf("%d\n", root->val);   // visit root first
    preorder(root->left);
    preorder(root->right);
}

Compare with inorder: the only difference is where the printf line appears — before or after the recursive calls.

Your Task

Implement void preorder(struct Node *root) that prints each node's value, visiting the current node first, then left, then right.