Yahoo Software Engineer 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

Write a select statement to retrieve work of all users who belong to my team.

• Join USERS and WORK tables on user_id

• Join MANAGERS and USERS tables on team

• Filter by manager_id

The manifest.json file contains the most important information of a Chrome extension.

• The manifest.json file includes the version number, permissions, content scripts, background scripts, and other important details.

• It is located in the root directory of the extension.

• It is required for all Chrome extensions.

• Example: "manifest_version": 2, "version": "1.0", "permissions": ["tabs", "storage"]

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

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

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

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

Print the level order traversal of binary tree in spiral form

• Perform level order traversal of the binary tree

• Alternate the direction of traversal for each level

• Use a stack to reverse the order of nodes in each level

• Print the nodes in the order of traversal

Find the maximum element in each subarray of size k in a given array.

• Iterate through the array from index 0 to n-k.

• For each subarray of size k, find the maximum element.

• Store the maximum elements in a separate array.

• Return the array of maximum elements.

To find the Kth largest element in two sorted arrays, we can use the merge step of merge sort algorithm.

• Merge the two arrays into a single sorted array using a modified merge sort algorithm.

• Return the Kth element from the merged array.

Merge two sorted arrays into one sorted array with expected time complexity of (m+n).

• Use a two-pointer approach to compare elements from both arrays and merge them into the first array.

• Start comparing elements from the end of both arrays and place the larger element at the end of the first array.

• Continue this process until all elements from the second array are merged into the first array.

The algorithm finds the position of the 3rd occurrence of 'B' in an n-ary tree from a given index in constant time complexity.

• Traverse the n-ary tree using a depth-first search (DFS) algorithm

• Keep track of the count of 'B' occurrences

• When the count reaches 3, return the current position

• If the end of the tree is reached before the 3rd 'B', return -1

Check if a given string is a composite of two words from a limited dictionary.

• Create a hash set of all the words in the dictionary.

• Iterate through all possible pairs of substrings in the given string.

• Check if both substrings are present in the hash set.

• If yes, return true. Else, return false.

Switch adjacent nodes in a single linked list.

• Traverse the linked list and swap adjacent nodes.

• Keep track of previous node to update its next pointer.

• Handle edge cases for first two nodes and last node.

• Example: 1->2->3->4 becomes 2->1->4->3.

Traverse only the left sub-tree of a binary search tree.

• Start at the root node

• If the left child exists, visit it and repeat the process

• If the left child does not exist, return to the parent node

• Continue until all nodes in the left sub-tree have been visited

Design an efficient data structure for two lifts in a building of n floors.

• Use a priority queue to keep track of the floors each lift is heading to

• Implement a scheduling algorithm to determine which lift to assign to a new request

• Consider adding a weight limit to each lift to prevent overloading

• Use a hash table to keep track of the current location of each lift

To find the maximum number that can be formed from the digits of an integer.

• Convert the integer to a string

• Sort the characters in descending order

• Join the sorted characters to form the maximum number

Reverse all the words in a given string

• Split the string into an array of words

• Loop through the array and reverse each word

• Join the reversed words back into a string

Explaining how to handle 'n' in a string during swapping process

• Identify the positions of 'n' in the string

• Exclude those positions from the swapping process

• Use a temporary variable to swap the characters

• Ensure the swapped characters are not 'n'

• Return the modified string

We can use any sorting algorithm like quicksort, mergesort, heapsort, etc.

• Choose the appropriate sorting algorithm based on the size of the file and the range of numbers

• Implement the chosen algorithm in the programming language of choice

• Read the numbers from the file into an array or list

• Apply the sorting algorithm to the array or list

• Write the sorted numbers back to the file

Word suggestions in Eclipse can be implemented using algorithms like Trie or N-gram models.

• Use Trie data structure to store the dictionary of words

• Implement auto-complete feature using Trie

• Use N-gram models to suggest words based on context

• Train the N-gram model on a large corpus of text data

• Combine both approaches for better accuracy

• Consider user's typing speed and frequency of words for better suggestions

To check if a number k lies in a sequence formed by adding previous 2 elements, start with a=0 and b=1 and iterate until k is found or exceeded.

• Start with a=0 and b=1

• Iterate through the sequence until k is found or exceeded

• If k is found, return true. If exceeded, return false

Check if a Binary Tree is a Binary Search Tree (BST)

• A BST has the property that all nodes in the left subtree of a node have values less than the node's value, and all nodes in the right subtree have values greater than the node's value

• We can traverse the tree in-order and check if the resulting sequence is sorted

• Alternatively, we can recursively check if each node satisfies the BST property

Keep track of kth largest number in a stream of numbers.

• Use a min-heap of size k to keep track of kth largest number.

• For each incoming number, compare it with the root of the heap.

• If it is larger than the root, replace the root with the new number and heapify.

• The root of the heap will always be the kth largest number.

Infix expression can be evaluated using the concept of operator precedence and associativity.

• Convert the infix expression to postfix expression using stack data structure

• Evaluate the postfix expression using stack data structure

• Use operator precedence and associativity rules to determine the order of evaluation

• Parentheses can be used to override the default order of evaluation