BST Find Maximum Element in DSA C++ - Execution Trace

Concept Flow - BST Find Maximum Element

Start at root node

↓

Check if right child exists?

No→Current node is max

Yes↓

Move to right child

↩Back to check right child

Start at the root and keep moving to the right child until there is no right child left. The last node visited is the maximum.

Execution Sample

DSA C++

Node* findMax(Node* root) {
  if (!root) return nullptr;
  while (root->right) {
    root = root->right;
  }
  return root;
}

This code finds the maximum element in a BST by moving right until no right child exists.

Execution Table

Step	Operation	Current Node	Right Child Exists?	Pointer Changes	Visual State
1	Start at root	50	Yes	current = 50	50 -> 30, 70
2	Move right	70	Yes	current = 70	50 -> 30, 70 -> 60, 80
3	Move right	80	No	current = 80	50 -> 30, 70 -> 60, 80
4	Return current as max	80	No	return 80	Max element found: 80

💡 No right child at node 80, so 80 is the maximum element.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
current	root (50)	50	70	80	80

Key Moments - 3 Insights

Why do we keep moving to the right child to find the maximum?

In a BST, all right children have values greater than their parent. So moving right leads to larger values. See execution_table steps 1 to 3 where current moves right.

What if the tree is empty (root is null)?

The function returns nullptr immediately (step 1 in code). No nodes to check means no maximum.

Why do we stop when there is no right child?

Because the node without a right child is the largest in that path. Execution_table step 3 shows current at 80 with no right child, so we stop.

Visual Quiz - 3 Questions

Look at the execution_table, what is the current node at step 2?

A 70

B 50

C 80

D 30

💡 Hint

Check the 'Current Node' column at step 2 in execution_table.

At which step does the condition 'Right Child Exists?' become No?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Right Child Exists?' column in execution_table.

If the root node had no right child, what would be the maximum element?

A The left child of root

B The root node itself

C Null (no max)

D The right child of root

💡 Hint

Refer to the concept_flow and execution_table step 1 where no right child means current node is max.

Concept Snapshot

BST Find Maximum Element:
- Start at root node
- Move right while right child exists
- Stop when no right child
- Current node is maximum
- Returns pointer to max node

Full Transcript

To find the maximum element in a Binary Search Tree (BST), start at the root node. Check if the current node has a right child. If yes, move to the right child and repeat. If no right child exists, the current node is the maximum. This works because in BSTs, right children always have greater values than their parents. If the tree is empty, return null. The code uses a loop to move right until no right child is found, then returns that node as maximum.