20+ Hike Software Developer Interview Questions and Answers

Reverse words in a string by reversing the order of words while maintaining spaces.

• Split the input string by spaces to get individual words

• Reverse the order of the words

• Join the reversed words with a single space in between

Calculate and display the student's initial letter followed by the integer part of their average marks.

• Calculate the average of the three marks provided for each student.

• Display the initial letter of the student's name followed by the integer part of the average marks.

• Round down the average to the nearest integer to get the integer part.

Find K largest elements in an unsorted array and return them in non-decreasing order.

• Sort the array in non-decreasing order

• Return the last K elements of the sorted array

Given a number represented as a string, find the smallest number greater than the original with the same set of digits.

• Sort the digits in non-increasing order to find the next greater number.

• Swap the last two digits to get the smallest greater number.

• If no greater number exists, return -1.

Return the level order traversal of a binary tree given in level order with null nodes represented by -1.

• Parse the input to create the binary tree using level order traversal

• Use a queue to perform level order traversal and print the nodes in the order visited

• Handle null nodes represented by -1 appropriately

Find the peak element in an array of integers.

• Iterate through the array and check if the current element is greater than its neighbors.

• Handle edge cases for the first and last elements of the array.

• Return the peak element found.

Calculate various statistical measures given a large sample of integers in the range [0, 255] using the provided frequency array.

• Iterate through the 'count' array to calculate minimum and maximum values.

• Calculate the mean by summing up all values and dividing by the total count.

• Find the median by sorting the sample and determining the middle element(s).

• Identify the mode by finding the element with the highest frequency.

• Ensure precision up to 5 decimal places in the output.

Given a BST and a target value, determine if there exist two unique elements in the BST such that their sum equals the target.

• Traverse the BST in-order to get a sorted array of elements.

• Use two pointers approach to find the pair sum in the sorted array.

• Keep track of visited elements to ensure uniqueness.

• Handle edge cases like null nodes and empty tree.

• Example: For input BST [20, 10, 35, 5, 15, 30, 42, -1, 13, -1, -1, -1, -1, -1, -1, -1] and K = 45, output true.

The task is to determine the number of islands present on a 2D grid after each query of converting water to land.

• Create a function that takes the grid dimensions, queries, and coordinates as input.

• For each query, convert the water at the given coordinates to land and update the grid.

• Use depth-first search (DFS) to find connected lands and count the number of islands.

• Return the number of islands after each query.

Merge two sorted arrays into one sorted array within the first array.

• Create a pointer for the last index of ARR1 and ARR2 to start merging from the end.

• Compare elements from both arrays and place the larger element at the end of ARR1.

• Continue this process until all elements are merged in sorted order within ARR1.

Reverse alternate levels of a perfect binary tree by reversing nodes at even levels starting from level 2.

• Traverse the tree in level order and store nodes at even levels in a separate list.

• Reverse the list of nodes at even levels.

• Update the tree with the reversed nodes at even levels.

• Repeat the process for alternate levels starting from level 2.

Design a Least Recently Used (LRU) cache data structure that supports get and put operations with capacity constraint.

• Use a combination of hashmap and doubly linked list to efficiently implement the LRU cache.

• Keep track of the least recently used item and update it accordingly when inserting new items.

• Ensure to handle the capacity constraint by evicting the least recently used item when the cache is full.

Compute In-Order, Pre-Order, and Post-Order traversals for a given Binary Tree with 'N' nodes.

• Implement tree traversal algorithms: In-Order, Pre-Order, and Post-Order.

• Use recursion to traverse the binary tree efficiently.

• Handle null nodes represented by -1 in the input.

• Follow the order of nodes as they appear in the level order traversal.

• Ensure the output is space-separated lists for each traversal type.

Implement a function to sort a rotated sorted array in increasing order without using the sort() function.

• Find the pivot element in the rotated sorted array.

• Split the array into two subarrays based on the pivot element.

• Sort each subarray separately.

• Merge the sorted subarrays to get the final sorted array.

Calculate and print the median after each new integer is added to the stream.

• Use two heaps - a max heap to store the smaller half of the numbers and a min heap to store the larger half.

• Keep the sizes of the two heaps balanced to efficiently calculate the median.

• If the total number of elements is odd, the median will be the top element of the max heap.

• If the total number of elements is even, the median will be the average of the top elements of the two heaps.

5 pirates must divide 100 gold coins based on ranking and rules.

• Pirate 1 proposes a distribution, all pirates (including the proposer) vote on it. If majority agree, coins are distributed. If not, Pirate 1 is thrown overboard and Pirate 2 proposes a new distribution.

• Pirates are ranked by seniority, with Pirate 1 being the most senior.

• Pirates prioritize staying alive over getting gold, but also want to maximize their share of gold.

• Example: Pirate 1 proposes 98 coins for himsel...read more

Producer-Consumer problem involves multiple threads sharing a common buffer. Producers add items to the buffer while consumers remove them.

• Producers and consumers need to synchronize their access to the shared buffer to avoid race conditions.

• Semaphores can be used to control access to the buffer. Two semaphores are used - one to track the empty slots in the buffer and one to track the filled slots.

• Producers increment the empty semaphore count when they add an item to the buff...read more

Characteristics of distributed file systems include scalability, fault tolerance, and data replication.

• Scalability: Distributed file systems can easily scale to accommodate a large amount of data and users.

• Fault tolerance: They are designed to continue functioning even if some components fail, ensuring high availability.

• Data replication: Data is often replicated across multiple nodes to ensure reliability and performance.

• Consistency: Distributed file systems must maintain con...read more

Analyzing usage history involves tracking user interactions, patterns, and trends to improve application performance.

• Collect and store user interaction data such as clicks, page views, and time spent on each feature.

• Use analytics tools to generate reports and visualize usage patterns.

• Identify popular features, user preferences, and areas for improvement based on usage data.

• Implement A/B testing to compare different versions of features and analyze user behavior.

• Utilize machin...read more

Synchronized blocks are needed in Java to ensure thread safety by allowing only one thread to access a block of code at a time.

• Prevents multiple threads from accessing critical sections of code simultaneously

• Ensures data consistency and prevents race conditions

• Improves performance by reducing contention for shared resources

• Example: synchronized block in a method that updates a shared variable

ConcurrentHashMap is a thread-safe implementation of the Map interface in Java.

• ConcurrentHashMap allows multiple threads to read and write to the map concurrently without causing any issues like deadlocks or data corruption.

• It achieves thread-safety by dividing the map into segments, each of which can be locked independently.

• ConcurrentHashMap is more efficient than using synchronized maps for concurrent access.

• Example: ConcurrentHashMap<String, Integer> map = new ConcurrentHa...read more

Design a file sharing mechanism between two users.

• Implement a secure login system for both users.

• Allow users to upload files to a shared server.

• Provide a way for users to view and download files shared by the other user.

• Implement access control to ensure only authorized users can access the shared files.