Northrop Grumman Interview Questions and Answers

Round duration - 60 minutes
Round difficulty - Easy

It comprised of general aptitude questions and two coding questions. It was an offline test.

Q1. 
N Queens Problem
Given an integer N, find all possible placements of N queens on an N x N chessboard such that no two queens threaten each other.
Explanation:
A queen can attack another queen if they ar...read more
Ans. 
The N Queens Problem involves finding all possible placements of N queens on an N x N chessboard where no two queens threaten each other.
• Use backtracking algorithm to explore all possible configurations.

• Keep track of rows, columns, and diagonals to ensure queens do not attack each other.

• Generate and print valid configurations where queens are placed safely.

• Consider constraints and time limit for efficient solution.

• Exam...read more
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Q2. 
Sort 0 1 2 Problem Statement
Given an integer array arr of size 'N' containing only 0s, 1s, and 2s, write an algorithm to sort the array.
Input:
The first line contains an integer 'T' representing the n...read more
Ans. 
Sort an integer array containing only 0s, 1s, and 2s in linear time complexity.
• Use three pointers to keep track of the positions of 0s, 1s, and 2s in the array.

• Iterate through the array and swap elements based on the values encountered.

• Achieve sorting in a single scan over the array without using any extra space.
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Round duration - 60 minutes
Round difficulty - Easy

After having a technical discussion about my CV. He gave me two questions to code.

Q1. 
Ninja and Substrings Problem Statement
Ninja has to determine all the distinct substrings of size two that can be formed from a given string 'STR' comprising only lowercase alphabetic characters. These su...read more
Ans. 
Find all unique contiguous substrings of size two from a given string.
• Iterate through the string and extract substrings of size two

• Use a set to store unique substrings

• Return the set as an array of strings
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Q2. 
Cycle Detection in a Singly Linked List
Determine if a given singly linked list of integers forms a cycle or not.
A cycle in a linked list occurs when a node's next points back to a previous node in the ...read more
Ans. 
Detect if a singly linked list forms a cycle by checking if a node's next points back to a previous node.
• Traverse the linked list using two pointers, one moving one step at a time and the other moving two steps at a time.

• If the two pointers meet at any point, there is a cycle in the linked list.

• If one of the pointers reaches the end of the list (null), there is no cycle.
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Round duration - 30 minutes
Round difficulty - Easy

This was supposed to be the HR round but out of surprise the interviewer started by giving me a question to code. 
After I approached this question with the right solution he just asked about my family. After that he said to wait. After half an hour the results were announced. A total of three students were hired and I was amongst one of them.

Q1. 
Balanced Parentheses Combinations
Given an integer N representing the number of pairs of parentheses, find all the possible combinations of balanced parentheses using the given number of pairs.
Explanati...read more
Ans. 
Generate all possible combinations of balanced parentheses for a given number of pairs.
• Use recursion to generate all possible combinations of balanced parentheses.

• Keep track of the number of open and close parentheses used in each combination.

• Return the valid combinations as an array of strings.
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Q1. Tell me about yourself.
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