ICON Interview Questions, Process, and Tips

Round duration - 120 minutes
Round difficulty - Medium

The Entire Test is held in HackerRank Platform. It has: 
2 coding questions (one easy and one medium)
2 output questions(medium)
2 Aptitude(easy)
1 general Computer science(medium)
It took me 30 min for each coding questions. I did not know that general question is related to bash commands.
Tips: Practice the Warmup questions in Hacker Rank.
Do some Basic aptitude questions.
Thorough with the basic C and C++ concepts

Q1. 
Binary Tree to Doubly Linked List
Transform a given Binary Tree into a Doubly Linked List.
Ensure that the nodes in the Doubly Linked List follow the Inorder Traversal of the Binary Tree.
Input:
The fi...read more
Ans. 
Convert a Binary Tree into a Doubly Linked List following Inorder Traversal.
• Perform Inorder Traversal of the Binary Tree to get the nodes in order.

• Create a Doubly Linked List by linking the nodes in the order obtained from Inorder Traversal.

• Return the head of the Doubly Linked List as the output.
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Q2. 
Unique Element in Array
Given an arbitrary array arr consisting of N non-negative integers where every element appears thrice except for one. Your task is to find the element in the array that appears onl...read more
Ans. 
Find the unique element in an array where every other element appears thrice.
• Use XOR operation to find the unique element.

• Iterate through the array and XOR each element to find the unique one.

• Return the unique element as the answer.
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Round duration - 60 minutes
Round difficulty - Medium

It's completely around the data structures. The questions are a bit tricky but once u think without any tension u can get through easily. The interviewer is helpful and gives u few hints if u catch them at the right point of time u got it. 
Tips: got through Data Structures and Algorithms Made Easy by Narasimha Karumanchi. It's a best book for the interviews.

Q1. 
Binary Tree Traversals Problem Statement
Given a Binary Tree with 'N' nodes, where each node holds an integer value, your task is to compute the In-Order, Pre-Order, and Post-Order traversals of the binar...read more
Ans. 
Implement a function to compute In-Order, Pre-Order, and Post-Order traversals of a Binary Tree given in level-order format.
• Parse the input level-order tree elements to construct the binary tree.

• Implement recursive functions for In-Order, Pre-Order, and Post-Order traversals.

• Return the traversals as lists of lists for each test case.
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Q2. 
Delete N Nodes After M Nodes in a Linked List
Given a singly linked list and two integers 'N' and 'M', traverse the linked list to retain 'M' nodes and then delete the next 'N' nodes. Continue this proces...read more
Ans. 
Traverse a linked list to retain 'M' nodes and then delete the next 'N' nodes, repeating until the end of the list.
• Create a function that takes the head of the linked list, 'N', and 'M' as input parameters.

• Traverse the linked list, retaining 'M' nodes and deleting the next 'N' nodes in each iteration.

• Update the pointers accordingly to skip 'N' nodes after retaining 'M' nodes.

• Repeat this process until the end of the lin...read more
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Round duration - 60 minutes
Round difficulty - Easy

The interviewer asked to put everything on the blackboard and write down the code of each and everything.

Question : Explain all the search algorithm you know with space and Time complexities. 
Answer : Linear search : It is a sequential search algorithm where the entire array is traversed till the desired element is not found. Time complexity is O(N) and auxiliary space is O(1). 
Binary search : In this algorithm, a sorted array is searched by repeatedly dividing the search interval in half. 
Steps : 
1. Initially the interval covers the whole array.
2. If the value to be searched is less than the item in the middle of the interval, narrow the interval to the lower half. Otherwise, narrow it to the upper half. 
3. The process is repeated until the value is found or the interval is empty.
Time complexity is O(log n) and auxiliary space is O(1) in case of iterative implementation.

Q1. 
Maximum Frequency Number Problem Statement
Given an array of integers with numbers in random order, write a program to find and return the number which appears the most frequently in the array.
If multip...read more
Ans. 
Program to find the number with maximum frequency in an array of integers.
• Create a dictionary to store the frequency of each number in the array.

• Iterate through the array and update the frequency count in the dictionary.

• Find the number with the maximum frequency in the dictionary and return it.

• If multiple elements have the same maximum frequency, return the one with the lowest index.
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