Olive Crypto Systems Blockchain Developer Interview Questions and Answers

Algorithm to find 2 numbers in an array whose sum is equal to a target integer

• Use a hash table to store the difference between target and each element in the array

• Iterate through the array and check if the current element exists in the hash table

• Return the pair of elements that sum up to the target integer

Hashtable is faster for finding an item than a sorted list.

• Hashtable has constant time complexity O(1) for finding an item.

• Sorted list has logarithmic time complexity O(log n) for finding an item.

• Hashtable uses hashing to directly access the item's location.

• Sorted list requires binary search to find the item's location.

• Hashtable is ideal for large datasets with frequent lookups.

• Sorted list is ideal for datasets that re...read more

JSON and XML are the most popular data interchange formats when using APIs.

• JSON (JavaScript Object Notation) is a lightweight format that is easy to read and write. It is widely used in web APIs.

• XML (Extensible Markup Language) is a more complex format that is also widely used in web APIs.

• Other formats include CSV (Comma Separated Values), YAML (YAML Ain't Markup Language), and Protocol Buffers.

Popular APIs for Social Commerce services

• Facebook Graph API for social media integration

• Instagram API for photo sharing and tagging

• Twitter API for real-time updates and customer engagement

• Pinterest API for product discovery and sharing

• Google Maps API for location-based services

• PayPal API for secure payment processing

Use a script to iterate through each HTML page, locate phone numbers, and update their format.

• Write a script using a programming language like Python or JavaScript to iterate through each HTML page

• Use regular expressions to locate phone numbers in the pages

• Update the format of the phone numbers as needed (e.g. adding country code, changing separators)

• Save the updated HTML pages with the new phone number format

Designing Google Suggest system

• I would start by analyzing user search patterns and frequently searched keywords

• Then, I would create a database of these keywords and their associated search results

• I would use indexing services to quickly retrieve relevant results for each keyword

• I would also implement machine learning algorithms to improve the accuracy of suggestions over time

Check if a number is a power of 2 and odd.

• To check if a number is a power of 2, use bitwise AND operator with the number and its predecessor. If the result is 0, it is a power of 2.

• To check if a number is odd, use modulus operator with 2. If the result is 1, it is odd.

• Example code in Python:

• def is_power_of_two(num):

• return num & (num - 1) == 0

• def is_odd(num):

• return num % 2 == 1

By introducing new menu items, optimizing pricing strategy, and improving the overall dining experience.

• Conduct a survey to understand the preferences of employees

• Introduce healthy and affordable meal options

• Offer discounts for bulk orders or loyalty programs

• Partner with local vendors to source fresh ingredients

• Improve the ambiance and seating arrangements

• Implement online ordering and delivery services

Reviewing 30 million ads from 42 languages in Google AdWords and rejecting non-compliant ads requires a systematic approach.

• Create a set of specific rules and guidelines for ad compliance

• Use automated tools to filter out ads that violate the rules

• Assign a team of reviewers to manually check the remaining ads

• Ensure that the reviewers are fluent in the languages of the ads they are reviewing

• Regularly update the rules and...read more

Find the intersection of two square images represented as trees based on color rules.

• A white node (W) intersects with another white node (W) results in W.

• A black node (B) intersects with another black node (B) results in B.

• A white node (W) intersects with a black node (B) results in W.

• A mixed node (M) will have 4 children representing the intersection of its quadrants.

Determine the order of alien alphabets using a sorted dictionary of words.

• Create a graph where each node is an alien character.

• Add directed edges based on the order of characters in the given words.

• Perform topological sorting on the graph to determine the order.

• Example: For words ['abc', 'ab'], 'c' comes after 'b'.

• Handle cases with multiple characters differing at the same position.

Multiple data structures are used to print nodes in a specific order. One data structure cannot be used alone.

• The given order suggests a depth-first search traversal of a tree-like structure.

• A stack can be used to keep track of the nodes to be visited.

• A queue can be used to store the children of a node in the order they are visited.

• An array can be used to store the nodes in the required order.

• A linked list can be used ...read more

Check if one string is a subsequence of another by verifying character order.

• A subsequence maintains the order of characters but not necessarily consecutiveness.

• Example: 'abc' is a subsequence of 'aebdc' (a, b, c appear in order).

• Example: 'abc' is NOT a subsequence of 'acb' (order is violated).

• To check, iterate through both strings and match characters sequentially.

Find largest pen using minimum comparisons with tops.

• Divide pens into two groups and compare largest pen from each group with largest top.

• Repeat the process with the group containing the largest pen until only one pen is left.

• The remaining pen is the largest pen.

• Total number of comparisons required is 2n-3.

Given n dice with 'a' sides and sum b, return no. of ways to obtain b. Optimize time and space complexity.

• Use dynamic programming to reduce time complexity

• Create a 2D array to store the number of ways to obtain each sum for each number of dice

• Use rolling arrays to optimize space complexity

• Example: n=2, a=6, b=7 -> 6 ways to obtain sum 7

• Example: n=3, a=4, b=8 -> 21 ways to obtain sum 8

Sort 128 GB data on 2 machines with 64 GB RAM each. Extend to 1000 machines.

• Use external sorting algorithm like merge sort or quick sort

• Divide data into smaller chunks and sort them individually

• Merge sorted chunks using additional RAM

• For 1000 machines, use distributed sorting algorithms like MapReduce or Hadoop

• Ensure data consistency and fault tolerance in distributed sorting

I am passionate about technology and have developed skills through self-learning and practical experience, making me a strong candidate.

• I have completed several online courses in programming languages like Python and Java, which have equipped me with essential coding skills.

• I have worked on personal projects, such as developing a web application that helps users track their fitness goals, showcasing my ability to apply...read more