Immediate Smaller element in an N-ary Tree

Given an element x, task is to find the value of its immediate smaller element. 

👁 Image

Example : 

Input : x = 30 (for above tree)
Output : Immediate smaller element is 25

Explanation : Elements 2, 15, 20 and 25 are smaller than x i.e, 30, but 25 is the immediate smaller element and hence the answer. 

Approach :

• Let res be the resultant node.
• Initialize the resultant Node as NULL.
• For every Node, check if data of root is greater than res, but less than x. if yes, update res.
• Recursively do the same for all nodes of the given Generic Tree.
• Return res, and res->key would be the immediate smaller element.

Below is the implementation of above approach : 

Immediate smaller element of 30 is 25

Complexity Analysis:

• Time Complexity : O(N), where N is the number of nodes in N-ary Tree. 
• Auxiliary Space : O(N), for recursive call(worst case when a node has N number of childs)