most common AMAZON coding interview questions

below is a list of the 15 most frequently asked questions in an Amazon interview 

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

Arrays

find the missing number in the array

Problem Statement

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You are given an array containing ‘n’ distinct numbers taken from the range 0 to ‘n’. Since the array has only ‘n’ numbers out of the total ‘n+1’ numbers, find the missing number.

Determine if the sum of two 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 two integers in the array whose sum is equal to the given value.

linked lists

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.

Copy linked list with arbitrary pointer

Problem Statement

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You are given a linked list where the node has two pointers. The first is the regular ‘next’ pointer. The second pointer is called ‘arbitrary_pointer’ and it can point to any node in the linked list.

Your job is to write code to make a deep copy of the given linked list. Here, deep copy means that any operations on the original list (inserting, modifying and removing) should not affect the copied list.

trees

Given a binary tree, perform a zigzag level order traversal

Problem Statement

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Given a binary tree, populate an array to represent its zigzag level order traversal. You should populate the values of all nodes of the first level from left to right, then right to left for the next level and keep alternating in the same manner for the following levels.

Determine if a binary tree is a binary search tree

Problem Statement

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Given a Binary Tree, figure out whether it’s a Binary Search Tree. In a binary search tree, each node’s key value is smaller than the key value of all nodes in the right subtree, and are greater than the key values of all nodes in the left subtree i.e. L < N < R.

strings

longest substring with no more than 'k' distinct characters

Problem Statement

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Given a string, find the length of the longest substring in it with no more than K distinct characters.

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.

dynamic programming

how many ways can you make change with coins and a total amount

Problem Statement

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Given coin denominations and total amount, find out the number of ways to make the change.

Math and stats

find kth permutation

Problem Statement

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Given a set of ‘N’ elements, find the Kth permutation.

Find all subsets of a given set of integers

Problem Statement

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You are given a set of integers and you have to find all the possible subsets of this set of integers.

backtracking

print balanced brace combinations 

Problem Statement

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Print all braces combinations for a given value 'N' so that they are balanced.

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.

sorting and searching

find 'k' closest points to the origin

Problem Statement

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Given an array of points in the a 2D plane, find ‘K’ closest points to the origin.

find the Top 'k' frequent numbers in an array

Problem Statement

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Given an unsorted array of numbers, find the top ‘K’ frequently occurring numbers in it.

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