100+ Full Stack Developer Interview Questions and Answers for Freshers

Find the maximum sum of a contiguous subarray within an array of integers.

• Iterate through the array and keep track of the maximum sum of subarrays seen so far.

• Use Kadane's algorithm to efficiently find the maximum subarray sum.

• Consider edge cases like all negative numbers in the array.

• Example: For input [-2, 1, -3, 4, -1], the maximum subarray sum is 4.

Return the middle element of a singly linked list, or the one farther from the head if there are even elements.

• Traverse the linked list with two pointers, one moving twice as fast as the other

• When the fast pointer reaches the end, the slow pointer will be at the middle

• If there are even elements, return the one pointed by the slow pointer

The minimum number of swaps required to sort a given array of distinct elements in ascending order.

• Use a hashmap to store the original indices of the elements in the array.

• Iterate through the array and swap elements to their correct positions.

• Count the number of swaps needed to sort the array.

Sort an array of strings based on a new alphabetical order starting with a given character.

• Iterate through the array of strings and compare each string based on the new alphabetical order starting with the given character.

• Use a custom comparator function to sort the strings according to the new alphabetical order.

• Return the sorted array of strings.

Count the total number of unique pairs in an array whose elements sum up to a given value.

• Use a hashmap to store the frequency of each element in the array.

• Iterate through the array and for each element, check if (Sum - current element) exists in the hashmap.

• Increment the count of pairs if the complement exists in the hashmap.

• Divide the count by 2 to avoid counting duplicates like (arr[i], arr[j]) and (arr[j], arr[i]) separately.

Find the row with the maximum number of 1's in a grid of 0's and 1's, returning the index of the row with the most 1's.

• Iterate through each row of the grid and count the number of 1's in each row

• Keep track of the row index with the maximum number of 1's seen so far

• Return the index of the row with the maximum number of 1's

Find the length of the longest duplicate substring in a given string.

• Iterate through all possible substrings of the input string.

• Use a rolling hash function to efficiently compare substrings.

• Store the lengths of duplicate substrings and return the maximum length.

Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette.

• Iterate through the buildings to find the critical points (start and end) of each building.

• Sort the critical points based on x-coordinate and process them to find the skyline.

• Merge consecutive horizontal segments of equal height in the output to ensure no duplicates.

Validate if a given binary tree is a Binary Search Tree (BST) or not.

• Check if the left subtree of a node contains only nodes with data less than the node's data.

• Check if the right subtree of a node contains only nodes with data greater than the node's data.

• Ensure that both the left and right subtrees are also binary search trees.

• Traverse the tree in an inorder manner and check if the elements are in sorted order.

• Recursively check each node's value against the range of values ...read more

Implement a function to delete a node from a Binary Search Tree and return the inorder traversal of the modified BST.

• Understand the properties of a Binary Search Tree (BST) - left subtree contains nodes with data less than the node, right subtree contains nodes with data greater than the node.

• Implement a function to delete the given node from the BST while maintaining the BST properties.

• Perform inorder traversal of the modified BST to get the desired output.

• Handle cases where...read more

Given an array of integers and a target sum, find all pairs of elements that add up to the target sum.

• Use a hashmap to store the difference between the target sum and each element as keys and their indices as values.

• Iterate through the array and check if the current element's complement exists in the hashmap.

• Return the pairs of elements that add up to the target sum in sorted order.

Check if a given string is a palindrome considering only alphanumeric characters.

• Remove non-alphanumeric characters from the input string.

• Compare the string with its reverse to check for palindrome.

• Handle edge cases like empty string or single character input.

Determine if a robot's movement path is circular on a 2D grid based on a given sequence of moves.

• Iterate through the sequence of moves and keep track of the robot's position and direction.

• Check if the robot returns to the starting position after completing the moves.

• Use a counter-clockwise rotation (L) and clockwise rotation (R) to update the direction of the robot.

• Use 'G' to move the robot one unit in the current direction.

Check if a string contains any permutation of another string as a substring.

• Iterate through str2 with a sliding window of length str1, check if any permutation of str1 is present.

• Use a hashmap to store the frequency of characters in str1 and str2 for comparison.

• If the frequencies of characters in the sliding window match the frequencies of characters in str1, return True.

Find all possible paths for a rat in a maze from start to finish, moving in 'U', 'D', 'L', 'R' directions.

• Use backtracking to explore all possible paths in the maze.

• Keep track of visited cells to avoid loops.

• Recursively try moving in all directions and backtrack when reaching dead ends.

• Return the valid paths in alphabetical order as an array of strings.

Account Statements Transcription is a full stack application for converting Excel sheets to SQL tables, fetching data in UI, and allowing downloads in various formats.

• Create a front-end interface for users to upload Excel sheets

• Develop a back-end system to convert Excel data into SQL tables

• Implement a query system to fetch data based on user needs in the UI

• Provide options for users to download data in Excel or Word formats

This question asks for the minimum number of trampoline jumps a person needs to make in order to reach the last shop in a mall.

• The shops in the mall are laid out in a straight line and each shop has a constant value representing the maximum distance it can be jumped to.

• The person starts at shop 0 and wants to reach the last shop, shop N-1.

• If it is impossible to reach the last shop, the function should return -1.

• The function should take the number of test cases, the number of ...read more

Given a sorted alien dictionary in an array of strings, determine the character order of the alien language.

• Iterate through the words in the dictionary to build a graph of character dependencies.

• Perform a topological sort on the graph to determine the character order.

• Return the character array representing the order of characters in the alien language.

Determine the maximum profit that can be achieved by selling stocks with at most two transactions.

• Iterate through the array and calculate the maximum profit that can be achieved by selling stocks at each day.

• Keep track of the maximum profit after the first transaction and the maximum profit after the second transaction.

• Return the maximum profit that can be achieved overall.

The task is to determine the left view of a binary tree, which consists of nodes visible when viewed from the left side.

• Traverse the binary tree level by level from left to right, keeping track of the first node encountered at each level.

• Use a queue to perform level order traversal and keep track of the level number for each node.

• Store the first node encountered at each level in a result array to get the left view of the binary tree.

Find the smallest substring in a given string that contains all characters present in another string.

• Use a sliding window approach to find the smallest window in S that contains all characters in X

• Keep track of the characters in X using a hashmap

• Move the window by adjusting the start and end pointers

• Return the smallest window found

Group anagrams in an array of strings based on their characters.

• Iterate through each string in the input array

• Sort the characters of each string and use the sorted string as a key in a hashmap to group anagrams

• Return the values of the hashmap as the grouped anagrams

Determine the minimum length of instruction sequence for a robot to reach a given target on an infinite number line.

• Start at position 0 with speed +1, update position and speed based on 'A' and 'R' instructions

• For each test case, find the shortest sequence of instructions to reach the target

• Consider both positive and negative positions for the robot

• Return the minimum length of instruction sequence for each test case

Develop a function to remove all instances of a given character from a string.

• Create a function that takes the input string and character to be removed as parameters.

• Iterate through each character in the input string and only add characters that are not equal to the given character to a new string.

• Return the new string as the output.

• Handle edge cases such as empty input string or character.

• Example: Input string 'hello world' and character 'o' should return 'hell wrld'.

The task is to determine if a given string of parentheses is balanced or not.

• Iterate through each character in the string and use a stack to keep track of opening parentheses

• If a closing parenthesis is encountered, check if it matches the top of the stack. If not, the string is not balanced

• If all parentheses are matched correctly and the stack is empty at the end, the string is balanced

The problem involves finding the number of ways to tile a 2xN board using 2x1 tiles.

• Use dynamic programming to solve the problem efficiently.

• Consider the base cases for N=1 and N=2 to build up the solution for larger N.

• Implement a recursive function with memoization to avoid redundant calculations.

• Keep track of the number of ways modulo 10^9 + 7 to handle large values of N.

• Test the solution with different values of N to ensure correctness.

Prisoners must devise a strategy to guess the color of their own hat based on the hats of others.

• Prisoners can agree on a strategy before the hats are assigned.

• One strategy is for each prisoner to count the number of hats of a certain color and use that information to guess their own hat color.

• Another strategy involves using parity to determine the color of their own hat.

• Prisoners can also use a signaling system to convey information about their hat color to others.