most common apple coding interview questions

 the 15 most asked questions in an apple interview 

For detailed solutions to each question, you can visit
Grokking the Coding Interview: Patterns for Coding Questions

Arrays

Determine if the sum of three integers is equal to the given value

Problem statement

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Given an array of integers and a value, determine if there are any three integers in the array whose sum equals the given value.

Find the smallest subarray whose sum is greater than or equal to a given value

Problem statement

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Given an array of positive numbers and a positive number ‘S’, find the length of the smallest contiguous subarray whose sum is greater than or equal to ‘S’. Return 0, if no such subarray exists.

linked lists

Add two integers

Problem statement

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Given the head pointers of two linked lists where each linked list represents an integer number (each node is a digit), add them and return the resulting linked list.

Merge two sorted linked lists

Problem statement

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Given two sorted linked lists, merge them so that the resulting linked list is also sorted.

trees

Determine if two binary trees are identical

Problem statement

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Given the roots of two binary trees, determine if these trees are identical or not. Identical trees have the same layout and data at each node.

Find the minimum depth of a binary tree

Problem statement

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Find the minimum depth of a binary tree. The minimum depth is the number of nodes along the shortest path from the root node to the nearest leaf node.

strings

Longest substring with no repeating characters

Problem statement

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Given a string, find the length of the longest substring which has no repeating characters.

Given a string, rearrange it so that no characters repeat

Problem statement

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Given a string, find if its letters can be rearranged in such a way that no two same characters come next to each other.

dynamic programming

Find the maximum sum of a subarray

Problem statement

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Given an array of positive numbers and a positive number ‘k’, find the maximum sum of any contiguous subarray of size ‘k’.

Math and stats

Happy number

Problem statement

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Any number will be called a happy number if, after repeatedly replacing it with a number equal to the sum of the square of all of its digits, leads us to number ‘1’. All other (not-happy) numbers will never reach ‘1’. Instead, they will be stuck in a cycle of numbers which does not include ‘1’.

backtracking

Find all sum combinations

Problem statement

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Given a positive integer, target, print all possible combinations of positive integers that sum up to the target number.

Graphs

Clone a directed graph

Problem statement

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Given the root node of a directed graph, clone this graph by creating its deep copy so that the cloned graph has the same vertices and edges as the original graph.

design

Implement a LRU cache

Problem statement

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Least Recently Used (LRU) is a common caching strategy. It defines the policy to evict elements from the cache to make room for new elements when the cache is full, meaning it discards the least recently used items first.

sorting and searching

Search in rotated array

Problem statement

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Search for a given number in a sorted array that has been rotated by some arbitrary number. Return -1 if the number does not exist. Assume that the array does not contain duplicates.

Merge overlapping intervals

Problem statement

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Given a list of intervals, merge all the overlapping intervals to produce a list that has only mutually exclusive intervals.

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