10+ PayPal SDE-2 Interview Questions and Answers

Find sum of elements in a sorted array less than or equal to each element in queries.

• Iterate through queries and for each query, find the sum of elements in arr less than or equal to the query element.

• Use binary search to efficiently find the index of the last element less than or equal to the query element.

• Keep track of cumulative sum while iterating through arr to avoid recalculating sums.

• Return the list of sums for each test case.

Find the minimum number of character deletions needed to make each character's frequency unique in a given string.

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

• Identify characters with the same frequency and calculate the minimum deletions needed to make them unique.

• Return the total minimum deletions for each test case.

The problem involves finding the number of distinct ways to climb to the N-th stair by taking one or two steps at a time.

• Use dynamic programming to solve this problem efficiently.

• The number of ways to reach the N-th stair is the sum of the number of ways to reach the (N-1)th stair and the (N-2)th stair.

• Handle large inputs by taking modulo 10^9+7 of the result.

• Example: For N=3, there are 3 ways to climb to the third stair: (0, 1, 2, 3), (0, 2, 3), and (0, 1, 3).

Reverse the letters of a string while keeping non-alphabet characters in their original position.

• Iterate through the string and store the non-alphabet characters in their original positions.

• Reverse the letters of the string using two pointers approach.

• Combine the reversed letters with the non-alphabet characters to get the final reversed string.

The task is to find the next greater element for each element in an array to its right, if no greater element exists, return -1.

• Use a stack to keep track of elements for which the next greater element is not found yet.

• Iterate through the array from right to left and pop elements from the stack until a greater element is found.

• Store the next greater element for each element in a separate array.

• If the stack is empty after iterating through the array, it means there is no greate...read more

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

• Use a three-pointer approach to partition the array into sections of 0s, 1s, and 2s.

• Iterate through the array and swap elements based on their values to achieve the sorting.

• Time complexity should be O(N) where N is the number of elements in the array.

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

• Traverse the tree level by level and keep track of the leftmost node at each level

• Use a queue for level order traversal and a map to store the leftmost nodes

• Print the values of the leftmost nodes stored in the map as the left view of the tree

Check if a given string is a palindrome or not.

• Iterate through the string from both ends and compare characters.

• If all characters match, return 1 indicating a palindrome.

• If any characters don't match, return 0 indicating not a palindrome.

Find and return the sum of all the left leaf nodes in a binary tree.

• Traverse the binary tree using depth-first search (DFS)

• Check if a node is a leaf node and a left child

• Sum up the values of all left leaf nodes

Find the median of two sorted arrays by merging them and calculating the median of the combined array.

• Merge the two sorted arrays into one sorted array.

• Calculate the median of the combined array based on the total number of elements.

• Return the median as the result.

Given a sorted array, find K integers closest to X, preferring smaller ones in case of same distance.

• Use binary search to find the closest element to X in the array.

• Maintain two pointers to expand around the closest element to find K closest elements.

• Compare distances and values to select the K closest elements, preferring smaller ones if distances are equal.

The problem involves determining the number of similar string groups in a given list of strings based on a specific criteria.

• Iterate through each pair of strings in the list and check if they are similar based on the given criteria.

• Use a hash set to keep track of visited strings to avoid counting duplicates in the same group.

• Consider implementing a function to check if two strings are similar by allowing at most one swap of characters.

• Count the number of distinct groups of si...read more

Approach to low-level system design involves understanding requirements, breaking down components, defining interfaces, and optimizing performance.

• Understand the requirements and constraints of the system

• Break down the system into smaller components/modules

• Define clear interfaces between components for communication

• Optimize performance by considering data structures, algorithms, and resource utilization