Apple Software Developer Intern Interview Questions, Process, and Tips

Round duration - 120 Minutes
Round difficulty - Medium

Round 1 was of 2 hours duration. 1 hour for MCQs (60 MCQs) and 1 hour for coding questions(3 Coding Questions). MCQs were aptitude based (Verbal + Data Interpretation + Quantitative Aptitude).

Q1. 
Reverse Linked List Problem Statement
Given a singly linked list of integers, return the head of the reversed linked list.
Example:
Initial linked list: 1 -> 2 -> 3 -> 4 -> NULL
Reversed link...read more
Ans. 
Reverse a singly linked list of integers and return the head of the reversed linked list.
• Iterate through the linked list and reverse the pointers to point to the previous node instead of the next node.

• Use three pointers to keep track of the current, previous, and next nodes while reversing the linked list.

• Update the head of the reversed linked list as the last node encountered during the reversal process.
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Q2. 
Minimum Jumps Problem Statement
Bob and his wife are in the famous 'Arcade' mall in the city of Berland. This mall has a unique way of moving between shops using trampolines. Each shop is laid out in a st...read more
Ans. 
Find the minimum number of trampoline jumps Bob needs to make to reach the final shop, or return -1 if it's impossible.
• Use Breadth First Search (BFS) to find the minimum number of jumps needed.

• Keep track of the visited shops to avoid revisiting them.

• If a shop has an Arr value of 0, it is impossible to reach the last shop.

• Return -1 if the last shop cannot be reached.
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Round duration - 150 Minutes
Round difficulty - Medium

Have to attempt 2 programming questions within 2:30 hours. Can take any time over the weekend. Relatively easy problems. Questions were long, but the solution code was small.

Q1. 
The Skyline Problem
Compute the skyline of given rectangular buildings in a 2D city, eliminating hidden lines and forming the outer contour of the silhouette when viewed from a distance. Each building is ...read more
Ans. 
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 and create a list of critical points (x, y) where the height changes.

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

• Merge consecutive horizontal segments of equal height to ensure no duplicates in the output.
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Q2. 
MergeSort Linked List Problem Statement
You are given a Singly Linked List of integers. Your task is to sort the list using the 'Merge Sort' algorithm.
Input:
The input consists of a single line contain...read more
Ans. 
Sort a Singly Linked List using Merge Sort algorithm.
• Implement the Merge Sort algorithm for linked lists.

• Divide the list into two halves, sort each half recursively, then merge them.

• Use a fast and slow pointer to find the middle of the list for splitting.

• Handle the base case of a single node or empty list.

• Example: Input: 4 3 2 1 -1, Output: 1 2 3 4
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Round duration - 240 Minutes
Round difficulty - Medium

Had to solve 1 programming question in 4 hours. It was in the morning on a weekend. The environment was not so good. It was a small institute and got very crowded. The platform was also buggy. but the question was not difficult. Was able to solve it in just 1 hour and leave.

Q1. 
Batch Photography Problem
Alex has acquired a machine that can photocopy photos in batches of a minimum size 'K'. Given 'N' photos with resolutions represented in an integer array photos, the machine prod...read more
Ans. 
Minimize maximum error by splitting photos into batches of size at least 'K'.
• Sort the array of resolutions in ascending order.

• Iterate through the array and calculate the error for each possible batch.

• Return the minimum possible maximum error found.
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Round duration - 30 Minutes
Round difficulty - Easy

It was in the afternoon. The interviewer basically asked me what technologies I have worked on. Checked my knowledge of those technologies with simple questions. Told me what I'll be working on if I get selected.

Q1. 
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.

• Maintain left pointer for 0s, right pointer for 2s, and current pointer for traversal.

• Example: If current element is 0, swap it with element at left pointer and increment both pointers.

• E...read more
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Round duration - 90 Minutes
Round difficulty - Hard

It was also in the afternoon. The interviewer was the member of the team I'll be working on if I get selected. He asked me some basic questions about related technologies.
Gave me 2-3 DS & Algo problems and asked me to solve them.

Q1. 
Array Sum Calculation
Calculate the sum of all elements in an array of length N.
Input:
Line 1: An integer N indicating the size of the array.
Line 2: N integers, the elements of the array, separated by ...read more
Ans. 
Calculate the sum of all elements in an array of length N.
• Iterate through the array and add each element to a running sum.

• Return the final sum as the output.
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Q2. 
Ninja and Alien Language Order Problem
An alien dropped its dictionary while visiting Earth. The Ninja wants to determine the order of characters used in the alien language, based on the given list of wor...read more
Ans. 
Determine the order of characters in an alien language based on a list of words.
• Create a graph where each character is a node and there is a directed edge from character 'a' to character 'b' if 'a' comes before 'b' in any word.

• Perform a topological sort on the graph to get the order of characters.

• Return the order as a string in lexicographical order.
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Round duration - 120 Minutes
Round difficulty - Hard

This round had 3 preety good questions to be solved under 2 hours . The first question was from Graphs and DSU , the second question was related to DP and the third one was from Recursion.

Q1. 
Most Stones Removed with Same Row or Column
On a 2-D plane, there are ‘N’ stones placed at some integer coordinate points. Each coordinate point can have at most one stone. A stone can be removed if it sh...read more
Ans. 
Given a 2-D plane with stones at integer coordinate points, find the maximum number of stones that can be removed by sharing the same row or column.
• Iterate through the stones and create a graph where stones in the same row or column are connected.

• Use depth-first search (DFS) to find connected components in the graph.

• The maximum number of stones that can be removed is the total number of stones minus the number of conne
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Q2. 
Gold Mine Problem Statement
You are provided with a gold mine, represented as a 2-dimensional matrix of size N x M with N rows and M columns. Each cell in this matrix contains a positive integer represent...read more
Ans. 
The task is to determine the maximum amount of gold a miner can collect by moving in allowed directions in a gold mine represented as a 2D matrix.
• Create a 2D DP array to store the maximum gold collected at each cell

• Iterate through the matrix from left to right and update the DP array based on the allowed directions

• Return the maximum value in the last column of the DP array as the final result
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Q3. 
All Possible Balanced Parentheses Problem Statement
Given a positive integer N, generate all possible sequences of balanced parentheses using N pairs of parentheses.
A sequence of brackets is called bala...read more
Ans. 
Generate all possible sequences of balanced parentheses using N pairs of parentheses.
• Use backtracking to generate all possible combinations of balanced parentheses.

• Keep track of the number of opening and closing parentheses used.

• Add opening parentheses if there are remaining, and add closing parentheses only if there are more opening parentheses than closing.

• Recursively generate all valid combinations.

• Return the list o
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Round duration - 60 Minutes
Round difficulty - Medium

This round had 2 questions from DSA. Both the questions were preety straightforward and were asked to check my implementation skills and how well do I handle Edge Cases for tricky problems.

Q1. 
Stack using Two Queues Problem Statement
Develop a Stack Data Structure to store integer values using two Queues internally.
Your stack implementation should provide these public functions:
Explanation:
...read more
Ans. 
Implement a stack using two queues to store integer values.
• Use two queues to simulate stack operations: push elements to one queue, then move all elements to the other queue to simulate pop and top operations.

• Maintain the size of the stack and check for empty stack using the size of the queues.

• Handle edge cases such as popping or getting top element from an empty stack.

• Ensure the implementation follows the specified pu...read more
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Q2. 
Rotate Matrix by 90 Degrees Problem Statement
Given a square matrix 'MATRIX' of non-negative integers, rotate the matrix by 90 degrees in an anti-clockwise direction using only constant extra space.
Inpu...read more
Ans. 
Rotate a square matrix by 90 degrees in an anti-clockwise direction using constant extra space.
• Iterate through each layer of the matrix and swap elements in groups of 4

• Transpose the matrix and then reverse each row to achieve the rotation

• Ensure to handle edge cases like odd-sized matrices
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Round duration - 60 Minutes
Round difficulty - Medium

This round also had 2 questions related to DSA where I was first expected to explain my approaches and then discuss the time and space complexities of my solution. After that , I was asked some core concepts related to OOPS and OS.

Q1. 
Triplets with Given Sum
Given an array ARR consisting of N integers, find all distinct triplets in the array that add up to a given number K.
Example:
Input:
T = 2
N = 5
ARR = [1, 2, 3, 4, 5]
K = 9
N = 4
...read more
Ans. 
Find all distinct triplets in an array that add up to a given number.
• Use three nested loops to iterate through all possible triplets.

• Sort the array first to easily skip duplicates.

• Use two-pointer technique to find the remaining element for each triplet.

• Handle edge cases like empty list or no triplet summing up to K.
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Q2. 
Trapping Rain Water Problem Statement
You are given a long type array/list ARR of size N, representing an elevation map. The value ARR[i] denotes the elevation of the ith bar. Your task is to determine th...read more
Ans. 
Calculate the total amount of rainwater that can be trapped between given elevations in an array.
• Iterate through the array and calculate the maximum height on the left and right of each bar.

• Calculate the amount of water that can be trapped at each bar by taking the minimum of the maximum heights on the left and right.

• Sum up the trapped water at each bar to get the total trapped water for the entire array.
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Q3. What is the Diamond Problem in C++ and how can it be resolved?
Ans. 
Diamond Problem is a multiple inheritance issue in C++ where a class inherits from two classes that have a common base class.
• Diamond Problem occurs when a class inherits from two classes that have a common base class, leading to ambiguity in accessing members.

• It can be resolved in C++ using virtual inheritance, where the common base class is inherited virtually to avoid duplicate copies of base class members.

• Example: c...read more
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Q4. What is thrashing in operating systems?
Ans. 
Thrashing in operating systems occurs when the system is spending more time swapping data between memory and disk than actually executing tasks.
• Occurs when the system is constantly swapping data between memory and disk

• Causes a decrease in system performance as it spends more time on swapping than executing tasks

• Usually happens when the system does not have enough physical memory to handle the workload efficiently
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Round duration - 30 Minutes
Round difficulty - Easy

This was my last round and I hoped it to go good just like the other rounds. The interviewer was very straight to point and professional. The interview lasted for 30 minutes.

Q1. What is something about you that is not included in your resume?
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Round duration - 60 minutes
Round difficulty - Easy

The round was taken on Cocubes platform with video enabled . The time I chose was 3:00 P.M.

Q1. 
Maximum Number from Linked List Problem Statement
Given a linked list where each node contains a single digit, your task is to construct the largest possible number using these digits.
Objective:
Print ...read more
Ans. 
Given a linked list of single digits, construct the largest number possible.
• Traverse the linked list to extract the digits

• Sort the digits in descending order

• Concatenate the sorted digits to form the maximum number
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Round duration - 60 Minutes
Round difficulty - Medium

The coding problems were medium and it was held online on Cocubes at 4:00 PM

Q1. 
Maximum Sum Path from Leaf to Root
Given a binary tree with 'N' nodes, identify the path from a leaf node to the root node that has the maximum sum among all root-to-leaf paths.
Example:
All the possibl...read more
Ans. 
Find the path from a leaf node to the root node with the maximum sum in a binary tree.
• Traverse the binary tree from leaf to root while keeping track of the sum of each path.

• Compare the sums of all paths and return the path with the maximum sum.

• Use recursion to traverse the tree efficiently.

• Consider negative values in the tree when calculating the sum of paths.
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Q2. 
Bipartite Graph Check
Determine if a given graph is bipartite. A graph is considered bipartite if its vertices can be divided into two disjoint sets, 'U' and 'V', such that every edge connects a vertex in...read more
Ans. 
Check if a given graph is bipartite by dividing its vertices into two disjoint sets.
• Create two sets 'U' and 'V' to divide the vertices

• Check if every edge connects vertices from different sets

• Use graph traversal algorithms like BFS or DFS to determine bipartiteness
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