Vigilant Technologies Interview Questions and Answers

90 minute test on hacker rank consisting of 3 coding questions all of medium difficulty. Most candidates are required to solve more than 1 question.

Q1. Questions on concepts of OOPS and Operating Systems.
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Q2. Find least common ancestor of a binary tree.
Ans. 
Find the lowest common ancestor of a binary tree.
• Traverse the tree recursively from the root node.

• If the current node is null or matches either of the given nodes, return the current node.

• Recursively search for the nodes in the left and right subtrees.

• If both nodes are found in different subtrees, return the current node.

• If both nodes are found in the same subtree, continue the search in that subtree.
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Q3. Find first missing positive integer from an array for non-negative integers.
Ans. 
Find first missing positive integer from an array of non-negative integers.
• Create a hash set to store all positive integers in the array

• Loop through the array and add all positive integers to the hash set

• Loop through positive integers starting from 1 and return the first missing integer not in the hash set
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Q1. Design a parking lot
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Design a parking lot
• Consider the size and capacity of the parking lot

• Decide on the layout and organization of parking spaces

• Implement a system to manage parking availability and reservations

• Include features like ticketing, payment, and security

• Consider scalability and future expansion
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Q1. Given a grid which represents an ocean( For all index i,j if mat[i][j] = 1 is island and mat[i][j] = 0 means water). Find the island with largest area.
Ans. 
Find the largest island area in a grid representing an ocean using DFS or BFS.
• Use Depth-First Search (DFS) or Breadth-First Search (BFS) to explore the grid.

• Mark visited cells to avoid counting them multiple times.

• Count the size of each island during the traversal.

• Example: For a grid [[1,0,0],[1,1,0],[0,0,1]], the largest island has area 3.

• Keep track of the maximum area found during the exploration.
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Q2. Given list of strings group them into distinct anagrams.
Ans. 
Group list of strings into distinct anagrams.
• Create a hash table with sorted string as key and list of anagrams as value.

• Iterate through the list of strings and add each string to its corresponding anagram list in the hash table.

• Return the values of the hash table as a list of lists.
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