OLX Sales Account Manager Interview Questions and Answers for Experienced

Design optimal data structures for LRU cache

• Use a doubly linked list to keep track of recently used items

• Use a hash table to store key-value pairs for quick access

• When an item is accessed, move it to the front of the linked list

• When the cache is full, remove the least recently used item from the back of the linked list and hash table

Convert a sorted array to balanced binary search tree

• Find the middle element of the array and make it the root of the tree

• Recursively construct the left subtree using the left half of the array

• Recursively construct the right subtree using the right half of the array

• Repeat until all elements are added to the tree

Reverse a singly linked list in groups of k in­place

• Divide the linked list into groups of k nodes

• Reverse each group of k nodes

• Connect the reversed groups to form the final linked list

A recursive routine to calculate a ^ n

• The base case is when n is 0, in which case the result is 1

• For any other value of n, the result is a multiplied by the result of a^(n-1)

• The recursive function should call itself with a^(n-1) as the new input

Design optimal data structure for never-ending stream of numbers for insertion, deletion, searching, kth largest and kth smallest.

• Use a balanced binary search tree like AVL or Red-Black tree for efficient insertion, deletion, and searching.

• Maintain two heaps, one for kth largest and one for kth smallest.

• For finding kth largest, use a min heap of size k and for kth smallest, use a max heap of size k.

• Alternatively, use a...read more

Search an element in sorted rotated array.

• Use binary search to find the pivot point where the array is rotated.

• Divide the array into two subarrays and perform binary search on the appropriate subarray.

• Handle the cases where the target element is at the pivot point or not present in the array.

Find the Kth largest element in an array.

• Sort the array in descending order and return the element at index K-1.

• Use a max heap to find the Kth largest element efficiently.

• Implement a quickselect algorithm to find the Kth largest element in linear time.

Reverse a linked list in groups of n elements.

• Divide the linked list into groups of n elements.

• Reverse each group individually.

• Connect the reversed groups to form the final linked list.

• Handle cases where the number of elements is not a multiple of n.

• Example: 1->2->3->4->5->6->7->8, n=3 -> 3->2->1->6->5->4->8->7

Find the median of two sorted arrays.

• Merge the two arrays into one sorted array and find the median.

• Use binary search to find the median in O(log(min(m, n))) time complexity.

• Handle edge cases like empty arrays or arrays of different lengths.

Count number of paths from (0, 0) to (m, n) in a matrix while crossing through some indexes were not allowed.

• Use dynamic programming to solve the problem

• Create a 2D array to store the number of paths

• Traverse the matrix and update the array based on the allowed paths

• Return the value at the last index of the array

The question asks to convert the leaves of a binary tree into a doubly linked list without using extra space.

• Traverse the binary tree in a depth-first manner

• When a leaf node is encountered, update its left and right pointers to form the doubly linked list

• Keep track of the previous leaf node to update its right pointer

• Return the head of the doubly linked list

Count number of ways to reach opposite corner of a m*n table moving in two directions only.

• Use dynamic programming to solve the problem

• The number of ways to reach a cell is the sum of the number of ways to reach the cell above it and the cell to the left of it

• The number of ways to reach the opposite corner is the number of ways to reach the cell in the last row and last column

• Example: For a 2*2 table, there are 2 ways ...read more

The number of ways to travel n steps by taking one or two steps at a time.

• This is a classic problem that can be solved using dynamic programming.

• The number of ways to travel n steps is equal to the sum of the number of ways to travel n-1 steps and n-2 steps.

• Use an array to store the number of ways for each step, starting with base cases for 0 and 1 steps.

• Iterate through the array to calculate the number of ways for eac...read more

Convert infix expression to postfix expression.

• Use a stack to keep track of operators.

• Iterate through the infix expression and push operands to output.

• If an operator is encountered, pop operators from stack until a lower precedence operator is found.

• Push the operator to stack.

• After iterating, pop remaining operators from stack and append to output.

• Reverse the output to get postfix expression.

Reverse a binary search tree while maintaining parent-child relationship.

• Start by swapping the left and right child of each node recursively.

• Use a depth-first search approach to traverse the tree.

• Make sure to update the parent-child relationships accordingly.

To find min and max element in stack in O(1), we can use an auxiliary stack.

• Create an auxiliary stack to keep track of the minimum and maximum elements.

• Push the first element to both the main and auxiliary stack.

• For each subsequent element, compare it with the top element of the auxiliary stack and push the smaller element to the auxiliary stack.

• To get the minimum element, simply return the top element of the auxiliary...read more

Given an array, find the next minimum element for each element.

• Iterate through the array

• For each element, compare it with the elements on its right

• Find the minimum element greater than the current element

• If no such element exists, assign -1

• Build the resultant array

Remove characters from string A that appear in string B, considering their frequency in B.

• Use a frequency counter for string B to track occurrences of each character.

• Iterate through string A and build a new string excluding characters found in B.

• Example: A = 'hello', B = 'l' -> Result: 'heo'.

• Example: A = 'banana', B = 'an' -> Result: 'b'.

• Consider edge cases like empty strings or no common characters.

Find median of input stream in minimum time complexity using online algorithm.

• Use two heaps, one max heap for elements smaller than current median and one min heap for elements greater than current median.

• Maintain balance between the two heaps by ensuring that the size difference is at most 1.

• If the size of both heaps is equal, median is the average of the top elements of both heaps. Else, median is the top element of ...read more

To make a copy of a linked list with two pointers, iterate through the original list and create a new node for each element.

• Iterate through the original linked list

• Create a new node for each element

• Set the 'next' pointer of each new node

• Set the 'arbitrary' pointer of each new node

Implementing caching, optimizing queries, and using CDNs can reduce latency when accessing data from social networking sites.

• Use caching mechanisms like Redis or Memcached to store frequently accessed data.

• Optimize database queries to reduce response time, e.g., using indexes.

• Implement pagination to load data in chunks instead of all at once.

• Utilize Content Delivery Networks (CDNs) to serve static assets closer to user...read more

Use a min-heap to efficiently find the m closest points to an origin in a coordinate system.

• 1. Use a min-heap (priority queue) to store points based on their distance from the origin.

• 2. Calculate the distance using the Euclidean formula: distance = sqrt((x2 - x1)^2 + (y2 - y1)^2).

• 3. Insert points into the heap and maintain its size to m to keep only the closest points.

• 4. Example: For points (1,2), (3,4), (5,6) and orig...read more

Reverse the nodes of a linked list in pairs of n

• Iterate through the linked list in pairs of n

• Reverse the nodes within each pair

• Connect the reversed pairs together

• Handle cases where the number of nodes is not a multiple of n

Find a number in a consecutive integer array using binary search for optimal time complexity.

• The array is sorted and consists of consecutive integers, e.g., [1, 2, 3, 4, 5].

• Use binary search to find the number in O(log n) time complexity.

• Calculate the mid index and compare the middle element with the target.

• If the target is less than the middle element, search the left half; otherwise, search the right half.

• Example: To...read more

To check if a singly linked list is a palindrome, reverse the second half and compare it with the first half.

• Traverse the linked list to find the middle node

• Reverse the second half of the linked list

• Compare the reversed second half with the first half to check for palindrome

Given a preorder of binary tree with leaf nodes represented by N, construct the tree.

• Start by creating an empty stack.

• Iterate through the preorder list.

• If the current element is N, create a leaf node and push it onto the stack.

• If the current element is not N, create a new node and set its left child to the top of the stack.

• Pop the top of the stack and set it as the right child of the new node.

• Push the new node onto the...read more

The question asks to find the maximum occupancy word in each line of a given multiline string and also count the occupancy of capital and small letters separately.

• Split the multiline string into individual lines

• For each line, split it into words

• Initialize variables to store the maximum occupancy word and its count

• Iterate through each word and count the occupancy of each letter

• If the current word has a higher occupancy ...read more

Validate user passwords against predefined conditions to ensure security and compliance.

• Password must be at least 8 characters long. Example: 'Password1' is valid, 'Pass' is invalid.

• Password must contain at least one uppercase letter. Example: 'Password1' is valid, 'password1' is invalid.

• Password must contain at least one lowercase letter. Example: 'Password1' is valid, 'PASSWORD1' is invalid.

• Password must include at l...read more

Algorithm to find the best buying and selling dates for maximum profit from given stock prices array.

• Iterate through the array and keep track of minimum price and maximum profit.

• If current price is less than minimum price, update minimum price.

• If current price minus minimum price is greater than maximum profit, update maximum profit and buying and selling dates.

• Return buying and selling dates.

• Example: [10, 7, 5, 8, 11,...read more

This task involves printing the elements of a matrix in a diagonal order, starting from the top-left corner.

• Iterate through each diagonal starting from the first row and the first column.

• For each diagonal, collect elements until you reach the bounds of the matrix.

• Print the collected elements for each diagonal in order.

• Example: For a 3x3 matrix [[1,2,3],[4,5,6],[7,8,9]], the output would be: 1, 2, 4, 3, 5, 7, 6, 8, 9.

The code finds the number of ways to reach n steps by jumping 1 or 2 steps at a time.

• Use dynamic programming to solve the problem

• Create an array to store the number of ways to reach each step

• Initialize the array with base cases for 0 and 1 steps

• Iterate through the array and calculate the number of ways for each step

• Return the value at the last step

Use divide and conquer to check for balanced parentheses by recursively splitting the string and validating each part.

• Divide the string into two halves until each substring is of length 1 or 0.

• Check the balance of each half recursively: count '(' and ')' in each half.

• Combine results: ensure that the total count of '(' matches ')' and that no half has more ')' than '(' at any point.

To find the index of a word in a billion-word dictionary, use binary search for O(log n) efficiency.

• Use binary search: Start with low = 0 and high = billion-1.

• Calculate mid = (low + high) / 2 and compare getWord(mid) with the target word.

• If getWord(mid) < target, search in the right half: low = mid + 1.

• If getWord(mid) > target, search in the left half: high = mid - 1.

• Repeat until low exceeds high or the word is f...read more

Inheritance isn't always the best choice; consider composition or interfaces for better flexibility and maintainability.

• Use composition: Create a new class that uses instances of the original class to access only the needed methods.

• Example: If you need methods A, B, and C from Class X, create Class Y that has an instance of Class X and calls only A, B, and C.

• Consider interfaces: Define an interface with the required me...read more

I'm seeking new challenges and opportunities for growth that align better with my career goals and aspirations.

• Desire for professional growth: I want to expand my skill set and take on more responsibilities.

• Cultural fit: I realized that the company's values and work environment don't align with my personal values.

• Career advancement: I am looking for a position that offers clearer paths for advancement and development.

• P...read more

Transform each node in a BST to the sum of all greater nodes, enhancing the tree's structure.

• Traverse the BST in reverse in-order (right, root, left) to access nodes in descending order.

• Maintain a running sum that accumulates the values of nodes visited.

• Update each node's value with the current running sum before moving to the left child.

• Example: For a BST with nodes 10, 5, 15, the transformation results in 25 (10 beco...read more

Finding the Lowest Common Ancestor (LCA) in an n-ary tree involves traversing the tree to identify shared ancestors.

• An n-ary tree is a tree data structure where each node can have at most n children.

• To find the LCA of two nodes, traverse the tree and store the path from the root to each node.

• Compare the paths to find the last common node.

• Example: In a tree with root A, children B and C, and C has children D and E, LCA ...read more

Amazon.com is an online retail giant with a vast selection of products and services.

• Advantages: Wide selection of products, competitive pricing, fast shipping, convenient shopping experience

• Disadvantages: Can put smaller retailers out of business, concerns over worker treatment and environmental impact

• Example: Amazon Prime offers free two-day shipping and access to streaming services like Prime Video and Music

• Example: ...read more

Use file locking mechanisms like flock or lockfile to make a file mutually exclusive on a shared file system.

• Use flock or lockfile to acquire a lock on the file before accessing it.

• Release the lock once the operation is complete.

• Ensure all processes accessing the file use the same locking mechanism.

• Example: flock /path/to/file -c 'command to execute'

• Example: lockfile /path/to/file && command to execute && rm -f /path/t...read more

I am a software developer with 5 years of experience in developing web applications using Java and JavaScript.

• 5 years of experience in software development

• Proficient in Java and JavaScript

• Developed web applications

• Strong problem-solving skills

• Experience with agile development methodologies

Positive: Strong problem-solving skills, Negative: Can be overly critical of own work

• Positive: Strong problem-solving skills - I excel at breaking down complex problems and finding efficient solutions

• Negative: Can be overly critical of own work - I tend to be perfectionistic and struggle with accepting imperfections

I had a failure in implementing a new feature due to a lack of understanding of the requirements.

• I was assigned to develop a new feature for our software application.

• I misunderstood the requirements and implemented the feature incorrectly.

• During the testing phase, it was discovered that the feature was not functioning as expected.

• I took responsibility for the mistake and immediately communicated it to my team lead.

• I wo...read more

Replace every element in array with its closest maximum element in right.

• Iterate through the array from right to left

• Keep track of the maximum element seen so far

• Replace each element with the maximum element seen so far

Designing a distributed Hashtable and discussing its pros and cons.

• Distributed Hashtable is a data structure that stores key-value pairs across multiple nodes.

• Pros include scalability, fault tolerance, and load balancing.

• Cons include increased complexity, potential for data inconsistency, and slower performance due to network communication.

• Examples of distributed Hashtable implementations include Cassandra, Riak, and D...read more

Resolving conflicts with a manager involves open communication, understanding perspectives, and finding common ground.

• Practice active listening to understand your manager's viewpoint before responding.

• Schedule a one-on-one meeting to discuss the conflict in a private setting.

• Use 'I' statements to express how the situation affects you, e.g., 'I feel overwhelmed when deadlines change suddenly.'

• Seek to understand the unde...read more

I prioritize open communication and collaboration to resolve conflicts effectively with my teammates.

• Listen actively to understand the other person's perspective.

• Use 'I' statements to express feelings without blaming others, e.g., 'I feel overwhelmed when deadlines are tight.'

• Seek common ground by identifying shared goals, such as delivering a successful project.

• Propose solutions collaboratively, encouraging input from...read more