# most common slack coding interview questions

## the 15 most asked questions in an slack interview

### Arrays

Find the missing number in the array

Problem statement

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

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

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

Copy linked list with arbitrary pointer

Problem statement

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

Level order traversal of a binary tree

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Problem statement

Given the root of a binary tree, display the node values at each level. Node values for all levels should be displayed on separate lines.

Determine if a binary tree is a binary search tree

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Problem statement

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

String segmentation

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Problem statement

Given a dictionary of words and an input string tell whether the input string can be completely segmented into dictionary words.

Reverse words in a sentence

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Problem statement

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

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Problem statement

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

### Math and stats

Find Kth permutation

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Problem Statement

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

Find all subsets of a given set of integers

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Problem statement

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

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

### Graphs

Clone a directed graph

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Problem statement

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 the High/Low index

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Problem Statement

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

Search rotated array

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Problem statement

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

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