40+ Interview Questions and Answers

Suggest a data structure for efficient search of a string in 10 files and print line number and file if string appears more than once.

• Use a hash table to store the file name and line number of each occurrence of the string.

• Iterate through each file and for each line, check if the string is present and update the hash table accordingly.

• Print the hash table entries for the string.

The task is to fill the 'next' field of each node in a binary tree to point to the next node at the same level.

• Use a level order traversal to process the tree nodes.

• Maintain a queue to store the nodes at each level.

• For each node, set its 'next' field to the next node in the queue.

• If a node is the last node at its level, set its 'next' field to NULL.

Given an infinite staircase with a broken kth step, find the maximum height we can reach in n rounds of jumping i steps.

• We can start by jumping the maximum number of steps in each round until we reach the broken step.

• After reaching the broken step, we can discard the i steps that would land us on the broken step and jump the remaining steps.

• We can continue this pattern until we reach the maximum height we can reach without stepping on the broken step.

To find anagrams of a given word in a dictionary, use a hash table to store sorted versions of each word as keys and their corresponding original words as values.

• Create a hash table to store the anagrams

• Iterate through each word in the dictionary

• Sort the characters of the word and use it as a key in the hash table

• If the key already exists, add the word to the list of values for that key

• Print the list of values for the given word's sorted characters

Find the nearest greater value of a given value in a Binary Search Tree (BST).

• Start from the root node and compare the given value with the current node's value.

• If the given value is less than the current node's value, move to the left subtree.

• If the given value is greater than the current node's value, move to the right subtree.

• Keep track of the closest greater value encountered while traversing the tree.

• Return the closest greater value found.

Function to check if a string of parenthesis is balanced

• Use a stack to keep track of opening parenthesis

• If a closing parenthesis is encountered, pop from stack and check if it matches

• If stack is empty and a closing parenthesis is encountered, return False

• If all parenthesis are matched and stack is empty, return True

Count the occurrences of words in a paragraph.

• Split the paragraph into words using whitespace as a delimiter.

• Create a dictionary to store the count of each word.

• Iterate through the words and increment the count in the dictionary.

• Return the dictionary with the word counts.

Find common elements out of two sorted array

• Use two pointers to traverse both arrays simultaneously

• Compare elements at each pointer and move the pointer of the smaller element

• If elements are equal, add to common elements list and move both pointers

• Stop when either pointer reaches end of array

Use a combination of sliding window and hashmap to find top k most visited website patterns by users

• Parse the csv file to extract user and website data

• Use a sliding window to generate all possible website patterns for each user

• Use a hashmap to count the frequency of each website pattern

• Sort the website patterns based on frequency and return the top k patterns

Boundary traversal of a tree is the process of visiting the nodes on the boundary of a tree in a specific order.

• The boundary traversal can be done in three steps: left boundary, leaf nodes, and right boundary.

• For the left boundary, start from the root and traverse down the left side of the tree until reaching a leaf node.

• For the leaf nodes, perform an inorder traversal to visit all the leaf nodes of the tree.

• For the right boundary, start from the rightmost leaf node and trave...read more

Convert a Binary Search Tree to a Doubly Linked List.

• Create a DLL node class with left, right, and data fields.

• Traverse the BST in-order and add each node to the DLL.

• Adjust the left and right pointers of each node to create the DLL.

• Return the head of the DLL.

Create a package dependency diagram based on object-oriented design principles.

• Identify the main classes/modules in the system

• Determine the relationships between classes/modules (e.g. inheritance, composition, aggregation)

• Visualize the dependencies between classes/modules using arrows or lines

• Consider using UML diagrams to represent the package dependency

The question is about balanced parenthesis and finding the maximum units on a truck.

• To check if a string of brackets is balanced, we can use a stack data structure.

• To find the maximum units on a truck, we need to sort the items by weight and then start adding them to the truck until it reaches its maximum capacity.

A question about finding nodes at a distance of K from a given node in a graph.

• Use BFS or DFS to traverse the graph and keep track of the distance from the starting node.

• Maintain a visited set to avoid revisiting nodes.

• Return all nodes at distance K from the starting node.

• Example: Find all nodes at distance 2 from node A in a graph.

Linked list is a data structure where each element points to the next element. Operations like insertion, deletion, traversal can be performed on linked lists.

• Linked list is a linear data structure where elements are stored in nodes. Each node contains data and a reference to the next node.

• Operations on linked list include insertion, deletion, traversal, and searching.

• For example, to insert a new node at the beginning of a linked list, create a new node with the data and poin...read more

Graph problems and popular algo implementations

• Shortest Path: Dijkstra's, Bellman-Ford, Floyd-Warshall

• Minimum Spanning Tree: Prim's, Kruskal's

• Topological Sorting: Kahn's, DFS

• Max Flow: Ford-Fulkerson, Edmonds-Karp

• Travelling Salesman Problem: Held-Karp, Christofides

• Graph Coloring: Greedy, Backtracking

Detect if a binary tree is symmetric.

• Check if the left and right subtrees are mirror images of each other.

• Use a recursive approach to compare corresponding nodes.

• Base case: if both nodes are null, return true.

• If one node is null and the other is not, return false.

• If the values of the nodes are not equal, return false.

• Recursively check if the left subtree of the left node is symmetric to the right subtree of the right node.

• Recursively check if the right subtree of the left nod...read more

The question is about advanced data structures and algorithms for a senior software engineer role.

• Focus on advanced data structures like AVL trees, B-trees, and tries

• Discuss complex algorithms like Dijkstra's algorithm, A* search algorithm, and dynamic programming

• Highlight experience with optimizing time and space complexity

• Provide examples of solving challenging coding problems or implementing complex algorithms

Finding the merge point of two linked lists.

• Traverse both linked lists to find their lengths.

• Move the pointer of the longer list ahead by the difference in lengths.

• Iterate both lists simultaneously until the merge point is found.

Traversing a linked list involves iterating through each node starting from the head until the end is reached.

• Start at the head node

• Iterate through each node by following the 'next' pointer until the end is reached

• Perform desired operations on each node as needed

DP + Sliding window problem

• Dynamic Programming (DP) is a technique to solve optimization problems by breaking them down into smaller subproblems

• Sliding window is a technique to solve problems by maintaining a window of elements in an array or string

• Combining DP and sliding window can be useful in solving problems that require both techniques

Treasury Island can be found using Depth First Search on a 2D array of strings.

• Implement a Depth First Search algorithm to traverse the 2D array of strings

• Start from a specific point on the island and explore all possible paths

• Keep track of visited cells to avoid infinite loops

• Return the path that leads to the treasury on the island

Recursively sum the values of nodes in a binary tree

• Use a recursive function to traverse the tree and add the values of each node

• Base case: if the current node is null, return 0

• Recursive step: return the sum of current node value, left subtree sum, and right subtree sum

Designing Amazon involves creating a user-friendly e-commerce platform with a vast product selection, efficient search and recommendation algorithms, secure payment processing, and reliable delivery logistics.

• Develop a user-friendly interface for easy navigation and product search

• Implement recommendation algorithms based on user behavior and preferences

• Integrate secure payment processing systems to protect customer information

• Establish efficient delivery logistics for timely ...read more

To invert a binary search tree (BST), swap the left and right children of each node recursively.

• Start from the root node and recursively swap the left and right children of each node.

• Repeat this process for all nodes in the BST.

• The final result will be the inverted BST.

Create a classic minesweeper game with a grid of cells to uncover without hitting any mines.

• Create a grid of cells with hidden mines randomly placed

• Allow the player to uncover cells and reveal numbers indicating nearby mines

• Implement logic to end the game if a mine is uncovered or all non-mine cells are revealed

Reverse a linked list

• Iterate through the linked list and change the direction of the pointers

• Use three pointers to keep track of current, previous and next nodes

• Recursively reverse the linked list

Count the number of islands in a 2D grid where '1' represents land and '0' represents water.

• Iterate through the grid and for each '1' encountered, perform a depth-first search to mark all adjacent '1's as visited.

• Increment the island count for each new island found.

• Ensure to handle boundary conditions and visited cells properly to avoid infinite loops.

Sorting linked lists involves rearranging the nodes in a specific order.

• Use a sorting algorithm such as merge sort or quick sort to rearrange the nodes in the linked list.

• Iterate through the linked list and compare each node with the next one to determine the correct order.

• Consider the time complexity of the sorting algorithm to ensure efficient sorting of the linked list.

Designing a bus transit system involves planning routes, schedules, stops, and ticketing systems.

• Consider the population density and traffic patterns of the area to determine the number and frequency of bus routes.

• Create a network of bus stops strategically located near residential areas, commercial centers, and transportation hubs.

• Implement a reliable ticketing system that allows for cashless payments and offers options for daily, weekly, and monthly passes.

• Integrate real-ti...read more

Subsequences of arrays are all possible combinations of elements in an array.

• A subsequence can be of any length, including 0 and the entire array.

• The order of elements in a subsequence must be maintained.

• The number of possible subsequences of an array of length n is 2^n.

• For example, the subsequences of [1, 2, 3] are [], [1], [2], [3], [1, 2], [1, 3], [2, 3], [1, 2, 3].

To troubleshoot a problem, identify the issue, gather information, analyze data, and implement a solution.

• Identify the problem by asking questions and gathering information

• Analyze data to determine the root cause of the problem

• Implement a solution by testing and verifying the fix

• Document the problem and solution for future reference