IBM Coding Questions with Answers 2024
IBM Coding Questions with Answers 2024

Coding interviews aren’t always hard to crack; creating a plan and being familiar with the systems can easily help you crack the interview and get a job in your desired company.

Today, we’ll be taking IBM coding questions with answers , where we will break down the IBM coding assessment round for you and help you land a job.

IBM is a well-known technology company in America, which means International Business Machines Corporation, headquartered in Armonk, New York, United States.

IBM is one of the most innovative companies with a valuable Brand ranking. There are multiple elements that you need to tackle in order to crack the coding round of IBM. Create a proper plan where you study technical topics and focus on the test input.

The second thing you can do is keep things simple, as people don’t like complexity. It’s your job to keep the code readable, and it should be understandable for the programmers.

IBM Coding Questions For Associate System Engineer 

Understand the important things first when you’re doing an interview; you need to be aware of the company and what they do. How they operate, and every other element of the company.

It’s okay to seek help, and being confident with your unfamiliarity with the topic doesn’t make you a bad candidate; ensure you’re relaxed throughout the rounds. Understand and review before you submit; it’s crucial to operate things patiently and check your code before you offer the solution.

Refactoring your code will only help you to understand what you can do better at it. Let’s understand the overall IBM coding questions process.

To give it to you directly, IBM asks for Coding Questions for their candidates, and the total time will be given to you is 55 minutes. The test is Non-Adaptive and doesn’t have any Negative Marking. To solve the problems, you need to be familiar with these languages, which are C, C++, JAVA, and Python.

IBM Coding Questions Test Duration

No. Of Questions For The Coding Round

 2 Coding questions

Type Of Test

Non-Adaptive test

Time Given

55 Minutes

Negative Marking

No Negative Marking

IBM Coding Questions with Answers 2024 (Updated).

  1. How to find the maximum subarray sum in an array of integers.

def max_subarray_sum(a):

  max_so_far = 0

max_ending_here = 0

for i in range(len(a)):

  max_ending_here = max(0, max_ending_here + a[i])

max_so_far = max(max_so_far, max_ending_here)

return max_so_far


To find the maximum subarray sum in an array of integers we have tackled two main variables which are :  max_so_far and max_ending_here. Both the elements represent the maximum subarray that has been going and the sum that ends at the current index. The algorithm here stats with initializing  max_so_far to 0 then iterates keeping track of max_ending_here. After the iterating process is completed it sends the value of max_so_far.


  1. A simple method to sort an array of integers in ascending and descending order.

def bubble_sort(a):

    for i in range(len(a) - 1):

        for j in range(len(a) - i - 1):

            if a[j] > a[j + 1]:

                a[j], a[j + 1] = a[j + 1], a[j]


The algorithm here works by consistently comparing the adjacent components which are present in the array and exchanging them to get them in the right order. The algorithm starts and iterates over it, comparing each component to its next one. If the present component is greater than its side one the algorithm exchanges them. The algorithm keeps repeating again and again until it’s sorted.


  1. The easiest way to find the shortest path between two nodes in a graph

def dijkstra(graph, source):

    distances = {}

    for node in graph:

        distances[node] = float("inf")

    distances[source] = 0

    queue = [source]

    while queue:

        current_node = queue.pop(0)

        for neighbor in graph[current_node]:

            new_distance = distances[current_node] + graph[current_node][neighbor]

            if new_distance < distances[neighbor]:

                distances[neighbor] = new_distance


    return distances


A priority queue is the main element in this function which helps us keep track of distances from sources to other nodes which are present in the graph. The algorithm adds a source node to the priority queue and the priority queue is distinguished by the distances of the nodes in the queue. Shortest distance of node from source node will be present at the front of the queue. The function here eliminates when the priority queue is emptying which tells us nodes present  in the graph have been traveled and their distances to the source node have been calculated.


  1. The space complexity of a binary search tree ?

    The space complexity of a binary search tree is O(n), where n is the number of nodes in the tree. This is because a binary search tree must store each node in the tree.


  2. What’s the time complexity of inserting an element into a Doubly linked list?

class Node:

    def __init__(self, data): = data = None
        self.prev = None

class DoublyLinkedList:

    def __init__(self):
        self.head = None
        self.tail = None

    def insert_at_beginning(self, data):
        new_node = Node(data) = self.head
        self.head = new_node

        if self.tail is None:
            self.tail = new_node
            self.head.prev = new_node

    def insert_at_end(self, data):
        new_node = Node(data)
        new_node.prev = self.tail
        self.tail = new_node

        if self.head is None:
            self.head = new_node
   = new_node

    def insert_at(self, index, data):
        if index == 0:
        elif index == len(self):
            new_node = Node(data)
            current_node = self.head
            for i in range(index - 1):
                current_node =

   = new_node
            new_node.prev = current_node
   = new_node


For this algorithm, we have inserted a new node at the start of the doubly linked list and at the end we’ve done the same. To get the index we insert a new node for the specified index. For the time complexity at the beginning and end we’ve inserted O(1) and at index O(n) where n is signified as the index.


  1. There’s a binary tree, check if it is a binary search tree or not.

class TreeNode:
    def __init__(self, data): = data
        self.left = None
        self.right = None

def is_bst(root):
    if root is None:
        return True

    if root.left is not None and >
        return False

    if root.right is not None and <
        return False

    return is_bst(root.left) and is_bst(root.right)


For the binary search tree check system, we’ve defined a function at first to check if it’s a binary search tree by recursively validating node values.


  1. Given a linked list, determine if it has a cycle.

def has_cycle(head):

    slow = head

    fast = head

    while fast is not None and is not None:

        slow =

        fast =

        if slow == fast:

            return True

    return False


For this code what we can do is create a function using the well-known Floyd’s Tortoise and Hare algorithm to check if a linked list has a cycle or not.


  1. There’s a string, determine if it is a palindrome or not.

def is_palindrome(string):

    string = string.lower()

    left = 0

    right = len(string) - 1

    while left < right:

        if string[left] != string[right]:

            return False

        left += 1

        right -= 1

    return True


Here we have implemented a function is_palindrome to check if the string is a palindrome or not. By using left and right pointers to compare the characters from start and end to the string moving towards the center.


  1. Given an array of integers, find the two numbers that add up to a given target sum.

def find_two_numbers_with_sum(array, target_sum):

    seen = set()

    for number in array:

        complement = target_sum - number

        if complement in seen:

            return (number, complement)


    return None


In this function, we’ve used find_two_numbers_with_sum element to find two numbers in an array that gives us a target addition. It uses a set to track numbers which are present while iterating from the array.


  1. How to find the kth largest element in an array in linear time gives a brief explanation.

def quickselect(array, k):

    if len(array) == 1:

        return array[0]

    pivot = array[random.randint(0, len(array) - 1)]

    less_than_pivot = []

    greater_than_pivot = []

    for element in array:

        if element < pivot:


        elif element > pivot:


    if k <= len(less_than_pivot):

        return quickselect(less_than_pivot, k)

    elif k > len(less_than_pivot) + 1:

        return quickselect(greater_than_pivot, k - len(less_than_pivot) - 1)


        return pivot


The above code uses the QuickSelect algorithm which helps us to find the k-th smallest element in an unordered list. Base Case, Pivot Selection, Partitioning, and Recursion are the four main elements which we use in this function to get the desired results.


  1. How do you check if a string is a palindrome or not?  Write a code and explain.

def is_palindrome(string):

    string = string.lower()

    reversed_string = string[::-1]

    return string == reversed_string


Here the algorithm is pretty easy as we’ve converted the input string to lowercase and then reverse the string and given a command to Returns True if the original string which is added is equal to its reverse, indicating a palindrome.


  1. Write a function to find the factorial of a number.

def factorial(number):

    if number == 0:

        return 1

    return number * factorial(number - 1)


For the factorial function we’ve used recursion to calculate the factorial of the number. The base case here is factorial(0) returns 1 and the recursive case here multiplies the number by the factorial of  – 1.


  1. Write a code to find out the greatest common divisor (GCD) of two numbers.

def gcd(a, b):

    while b != 0:

        a, b = b, a % b

    return a


To get the Greatest Common Divisor we’ve used the Euclidean Algorithm mixed with a while loop. The algorithm then Swaps and calculates the remainder until the number at the second position becomes zero. Then it returns the answer


  1. How you reverse a linked list ?

def reverse_linked_list(head):

    if head is None or is None:

        return head

    new_head = None

    while head is not None:

        next = = new_head

        new_head = head

        head = next

    return new_head


For the reverse linked list we Iteratively reverse a linked list by adjusting its given pointers. We Use three pointers head, new_head, and next in the program to reverse the links.


  1. Write a function to clone a linked list ?

def clone_linked_list(head):

    if head is None:

        return None

    new_head = Node(

    current = head

    new_current = new_head

    while is not None:

        new_node = Node( = new_node

        new_current = new_node

        current =

    return new_head


For a Clone Linked List we Create a new linked list with mixing nodes which have the same data as the original linked list present. Then it Iterates through the original list, making new nodes for each.

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  1. Write a function to find the lowest common ancestor of two nodes in a binary tree.

def lowest_common_ancestor(root, p, q):

    if root is None or root == p or root == q:

        return root

    left = lowest_common_ancestor(root.left, p, q)

    right = lowest_common_ancestor(root.right, p, q)

    if left and right:

        return root

    return left or right


For this code to get the Lowest Common Ancestor in a Binary Tree we Recursively find the lowest common ancestor of two nodes in a binary tree. Then it returns the root when it comes forward to a node and mixes the results from left and right subtrees.


  1. Write a code and explain the easiest way to check if a binary tree is balanced or not.

def is_balanced(root):

    if root is None:

        return True

    left_height = height(root.left)

    right_height = height(root.right)

    return (
        abs(left_height - right_height) <= 1
        and is_balanced(root.left)
        and is_balanced(root.right)


For the Balanced Binary Tree Check algorithm we first Recursively checks if a binary tree is balanced or not. Then we compare the heights of the left and right subtrees and make sure that their difference is at most 1.


  1. Write a function to find the k largest elements in an array of integers.

import heapq

def find_k_largest_elements(arr, k):
    heap = []
    for num in arr:
        heapq.heappush(heap, num)
        if len(heap) > k:
    return sorted(heap, reverse=True)

# Test the function with an example
arr = [3, 5, 2, 4, 1]
k = 3
print(find_k_largest_elements(arr, k))  # Output: [5, 4, 3]


For the largest element in the array a function header is given and it would involve sorting the array and returning the elements.


  1. How you delete a node from a linked list ?

def delete_node(head, node):
    Deletes a node from a linked list.

        head: The head of the linked list.
        node: The node to delete.

        The head of the linked list after the node has been deleted.

    if head == node:
        head =
        return head

    previous_node = None
    current_node = head

    while current_node != node:
        previous_node = current_node
        current_node =

    if current_node is None:
        return head =

    return head


First up if the node which is to be deleted is head then we update the head to the next node and return to the new head. If it’s not head we traverse the list until we find the node to delete.  The next pointer will be updated of the previous node to skip the node which is to be deleted in the code.


  1. Given a graph, check if it is bipartite. 

def is_bipartite(graph):

    colors = {}

    for node in graph:

        if node not in colors:

            colors[node] = 0

        if colors[node] == 1:

            for neighbor in graph[node]:

                if neighbor in colors and colors[neighbor] == 1:

                    return False

        for neighbor in graph[node]:

            if neighbor not in colors:

                colors[neighbor] = 1 - colors[node]

    return True


The color nodes of a graph with two colors is 0 and 1 and adjacent nodes have very different colors. Here we use a dictionary which is of colors to store the color of every node that is present to have different colors. By checking if the coloring is valid by ensuring no adjacent nodes have the same color in the code. Then we Return True if the graph is bipartite and False is not.

IBM Coding Assessment Related FAQs

Q: How to Crack IBM coding test?

A: The only way to study for the IBM coding assessment is by practicing your skillsets and solving the IBM Coding questions.

Q: How long is the IBM coding assessment?

A: The IBM coding test is 55 minutes long, where you have to solve two coding problems the interviewer gave.

Q: What are common IBM coding questions?

A: Above are the IBM coding questions that can be asked for IBM coding round, and everything around Data Structures and Python can be a part of it. 

Q: How do I prepare for IBM Coding Test?

A: By solving the above given IBM coding questions, you can easily prepare for the IBM coding assessment. 


In this blog post, we explored some commonly asked IBM coding questions and provided detailed answers. Remember, the key to acing coding interviews is practice. Make sure to understand the underlying concepts behind these questions and try solving them on your own before referring to the answers. Good luck with your interview preparation, and happy coding!

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