Write a program to find the deepest node in a binary tree?

Question: Given the root pointer to a binary tree, find the deepest node.

Input: Sample Tree (Pointer to node 1 is given).
Output: 5

According to the definition, the deepest node in a binary tree is the last element in the binary tree while performing a level order traversal. In the above case, therefore we have “5” as the deepest node in the tree.

We can simply follow a level order traversal approach to solve this problem. Just return the last element to get the deepest node.

Here is the implementation:-

#include<stdio.h>
#include<malloc.h>

struct binaryTreeNode{
	int data;
	struct binaryTreeNode * left;
	struct binaryTreeNode * right;
};

struct binaryTreeNode * deepestNode(struct binaryTreeNode * root)
{
	// Level order traversal
	struct binaryTreeNode * temp = NULL;
	struct queue * Q = NULL;

	if(root == NULL)
		return;
	Q = enQueue(Q, root);
	while(!isQueueEmpty(Q))
	{
		temp = Q -> front -> data;
		Q = deQueue(Q);
		if(temp -> left)
			Q = enQueue(Q, temp -> left);
		if(temp -> right)
			Q = enQueue(Q, temp -> right);
	}
	// Delete the queue
	free(Q);
	
	// Now return the last node
	return temp;
}

Time Complexity:- O(n)
Space Complexity:- O(n)

Ideone link for the running code:- http://ideone.com/tln1QD