20+ Vertiv Interview Questions and Answers

Count the number of rectangles (excluding squares) that can be formed on an N x N chessboard.

• Calculate total rectangles using formula N*(N+1)*M*(M+1)/4 where M = N-1

• Subtract the number of squares (N*(N+1)*(2*N+1)/6) from total rectangles

• Return the count modulo 1000000007 for each test case

Reverse words in a string word by word, removing leading/trailing spaces and extra spaces between words.

• 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

• Remove any leading or trailing spaces

Implement a function to solve a Sudoku puzzle by filling empty cells with valid numbers.

• Iterate through each empty cell and try filling it with a valid number (1-9) that satisfies Sudoku rules.

• Use backtracking to backtrack and try different numbers if a cell cannot be filled with a valid number.

• Check rows, columns, and 3x3 sub-grids to ensure each digit appears only once.

• Recursively solve the puzzle until all empty cells are filled with valid numbers.

Given finish times of horses, determine fastest horse in specified lane ranges for multiple queries.

• Iterate through each query and find the minimum finish time within the specified range of horses.

• Use a nested loop to handle multiple test cases and queries efficiently.

• Ensure to handle edge cases like empty ranges or invalid inputs.

• Consider using a data structure like arrays to store finish times and process queries.

Rearrange words in a sentence based on increasing order of their length.

• Split the sentence into words and calculate the length of each word.

• Sort the words based on their lengths in increasing order.

• If two words have the same length, maintain their original order from the input sentence.

Check if a valid Sudoku solution exists for a given 9x9 matrix with empty cells.

• Iterate through each row, column, and sub-matrix to ensure all digits from 1 to 9 appear exactly once.

• Use sets to keep track of digits seen in each row, column, and sub-matrix.

• If any digit is repeated in a row, column, or sub-matrix, return 'no'.

• If all rows, columns, and sub-matrices pass the validity check, return 'yes'.

Design a data structure to find the kth largest number in a continuous stream of integers.

• Design a specialized data structure to handle continuous stream of numbers

• Implement add(DATA) function to add integers to the pool

• Implement getKthLargest() function to retrieve the kth largest number

• Maintain the pool of numbers and update it based on queries

• Output the kth largest number for each Type 2 query

Find the node where two linked lists merge.

• Traverse both lists to find their lengths and the difference in lengths.

• Move the pointer of the longer list by the difference.

• Traverse both lists simultaneously until they meet at the merging node.

Calculate the distance between two nodes in a binary tree.

• Traverse the tree to find the paths from the root to each node

• Find the lowest common ancestor of the two nodes

• Calculate the distance by adding the distances from the LCA to each node

The task is to find the smallest number greater than the given number with the same set of digits.

• Iterate from right to left to find the first digit that can be swapped with a smaller digit to make the number greater.

• Swap this digit with the smallest digit to its right that is greater than it.

• Sort all digits to the right of the swapped digit in ascending order to get the smallest number greater than the original.

• If no such number exists, return -1.

• Example: For input '56789', ...read more

Sort an array of 0s, 1s, and 2s in increasing order.

• Use a three-pointer approach to sort the array in a single pass.

• Initialize three pointers for 0, 1, and 2 values and iterate through the array.

• Swap elements based on the values encountered to achieve the sorted array.

Find the shortest path in a binary matrix from a source cell to a destination cell consisting only of 1s.

• Use Breadth First Search (BFS) algorithm to find the shortest path.

• Keep track of visited cells to avoid revisiting them.

• Update the path length as you traverse the matrix.

• Return -1 if no valid path exists.

Find the most frequent word in a paragraph that is not in the list of banned words.

• Split the paragraph into words and convert them to uppercase for case-insensitivity.

• Count the frequency of each word, excluding banned words.

• Return the word with the highest frequency in uppercase.

Count the number of subarrays in an array whose XOR is equal to a given value.

• Iterate through the array and keep track of XOR values and their frequencies using a hashmap.

• For each element, calculate the XOR with the previous elements to find subarrays with XOR equal to the given value.

• Use the hashmap to efficiently count the number of subarrays with the desired XOR value.

• Handle edge cases like XOR value being 0 separately.

• Time complexity can be optimized to O(N) using a hashm...read more

Implement a stack using two queues to store integer values with specified functions.

• Use two queues to simulate stack operations efficiently.

• Maintain the top element in one of the queues for easy access.

• Ensure proper handling of edge cases like empty stack or invalid operations.

• Example: Push elements 5, 10, 15; Pop element 15; Check top element 10; Check size of stack; Check if stack is empty.

Implement a function to remove the Kth node from the end of a singly linked list.

• Traverse the list to find the length 'N' of the linked list.

• Calculate the position of the node to be removed from the beginning as 'N - K + 1'.

• Traverse the list again and remove the node at the calculated position.

Design and implement a data structure for LRU Cache to efficiently support get and put operations.

• Implement a doubly linked list to maintain the order of recently used keys.

• Use a hashmap to store key-value pairs for quick access.

• Update the linked list and hashmap accordingly for get and put operations.

• Discard the least recently used item when the cache reaches its capacity.

• Handle edge cases like key not found in cache.

• Example: Initialize cache with capacity 3, perform get and...read more

Implement a function to populate next right pointers in a complete binary tree.

• Traverse the tree level by level using BFS

• For each node, set its next pointer to the next node in the same level

• Handle null nodes appropriately by setting next pointer to null

• Ensure the tree is a complete binary tree to guarantee correct output

Find pairs of elements in an array that sum up to a given value, sorted in a specific order.

• Iterate through the array and for each element, check if the complement (S - current element) exists in a hash set.

• If the complement exists, add the pair to the result list.

• Sort the result list based on the criteria mentioned in the problem statement.

Given a string, find the longest palindromic substring, choosing the one with the smallest start index if multiple exist.

• Iterate through the string and expand around each character to find palindromes

• Keep track of the longest palindrome found and its starting index

• Return the longest palindromic substring with the smallest start index