[Solved] You need to visit all nodes of a binary tree in the order: root node first, then... Which algorithmic approach guarantees this traversal order efficiently without extra space for recursion or stack? | Tree: Depth-First Search

Tree: Depth-First Search - Binary Tree Preorder Traversal

You need to visit all nodes of a binary tree in the order: root node first, then recursively the left subtree, followed by the right subtree. Which algorithmic approach guarantees this traversal order efficiently without extra space for recursion or stack?

APostorder traversal using two stacks

BLevel-order traversal using a queue

CMorris preorder traversal using threaded binary tree

DInorder traversal using recursion

Step-by-Step Solution

Solution:

Step 1: Understand traversal order requirement
The problem requires visiting root before left and right subtrees, which is preorder traversal.
Step 2: Identify approach with no extra space
Morris preorder traversal uses threaded binary trees to achieve preorder traversal without recursion or stack, thus optimal in space.
Final Answer:
Option C -> Option C
Quick Check:
Preorder visits root first; Morris traversal achieves this with O(1) space [OK]

Quick Trick: Preorder visits root before children [OK]

Common Mistakes:

MISTAKES

Confusing inorder or postorder with preorder traversal
Assuming recursion is always needed
Using level-order which visits nodes by depth

Trap Explanation:

PITFALL

Many candidates think recursion or stack is mandatory, overlooking Morris traversal's O(1) space advantage.

Interviewer Note:

CONTEXT

Tests if candidate recognizes preorder traversal pattern and optimal approach beyond recursion.

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More Tree: Depth-First Search Quizzes

Which algorithmic approach guarantees this traversal order efficiently without extra space for recursion or stack?

Step 1: Understand traversal order requirement

Step 2: Identify approach with no extra space

Final Answer:

Quick Check:

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