Facebook Data Engineer Interview Questions and Answers

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 ri...read more

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 cl...read more

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 wit...read more

Construct a binary tree of height h and merge bottom nodes to create a cone-like structure.

• A binary tree of height h has 2^h - 1 nodes.

• Start combining leaf nodes from the bottom level upwards.

• Each combination can be visualized as merging two nodes into one.

• For example, if h=3, the tree has 7 nodes, and you combine nodes at levels 2 and 1.

• The final structure resembles a cone as nodes are merged.

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

Implement a function to sum two linked lists representing numbers and return the result as a linked list.

• Define a ListNode class to represent each node in the linked list.

• Traverse both linked lists simultaneously, adding corresponding digits.

• Handle carry-over when the sum of two digits exceeds 9.

• Create a new linked list to store the result.

• Example: For lists 2 -> 4 -> 3 and 5 -> 6 -> 4, the result is 7 ->...read more

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

Check if a string of parentheses is valid by ensuring every opening has a corresponding closing parenthesis.

• Use a stack to track opening parentheses. Example: '(()' -> push '(', push '(', pop ')' -> stack: ['('].

• For each closing parenthesis, check if there's a matching opening. Example: '()[]{}' -> valid, '([)]' -> invalid.

• At the end, the stack should be empty for a valid string. Example: '((()))' -> val...read more

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 ...read more

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.

Amazon is the right place for me because of its innovative culture, vast resources, and opportunities for growth.

• Amazon's innovative culture aligns with my passion for pushing boundaries and finding creative solutions.

• The company's vast resources provide the necessary tools and support to develop and deliver high-quality software.

• Amazon offers numerous opportunities for growth and career advancement, allowing me to con...read more

Find the row with the maximum number of zeroes in a sorted binary matrix.

• Iterate through each row of the matrix.

• Count the number of zeroes in each row.

• Keep track of the maximum count and the corresponding row index.

• Return the row index with the maximum zeroes.

• Example: For matrix [[0,0,1],[0,1,1],[1,1,1]], row 0 has 2 zeroes.