PayPal Full Stack Developer Interview Questions and Answers

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 threaten each other.

• Generate valid configurations recursively and backtrack when a solution is not possible.

The task is to determine the total number of ways to pair up 'N' friends or leave some of them single.

• Use dynamic programming to solve the problem efficiently.

• Consider the base cases when N is 1, 2, and 3 to derive the general formula.

• The result should be computed modulo 10^9 + 7 to handle large outputs.

Given a string, rearrange its characters so that no two adjacent characters are the same. Return 'Yes' if possible, 'No' otherwise.

• Iterate through the string and count the frequency of each character

• Use a priority queue to rearrange characters based on frequency

• Check if the rearranged string has no two adjacent characters the same

• Return 'Yes' if possible, 'No' otherwise

Group anagrams in a list of strings together and return each group as a list of strings.

• Iterate through the list of strings and sort each string alphabetically to create a key for grouping.

• Use a hashmap to store the sorted string as key and the original string as value.

• Return the values of the hashmap as the grouped anagrams.

Divide two integers without using multiplication, division, and modular operators, returning the floored value of the quotient.

• Implement division using bit manipulation and subtraction

• Handle edge cases like negative numbers and overflow

• Return the floored value of the quotient

Perform vertical order traversal of a binary tree based on decreasing 'Y' coordinates.

• Traverse the binary tree level by level and maintain the position of each node

• Use a map to store nodes at each position and sort them based on 'Y' coordinates

• Print the nodes in sorted order for each position to get the vertical order traversal