Huge collection of Array Interview Questions

An array is a data structure consisting of a collection of elements (values or variables), each identified by at least one array index or key. The simplest type of data structure is a linear array, also called a one-dimensional array.

Arrays are among the oldest and most important data structures and are used by almost every program. They are also used to implement many other data structures, such as lists, heaps, hash tables, deques, queues, stacks, strings.

An array as 10 boxes numbered 0 through 9; an index of 0

In this post, we have listed out commonly asked interview questions that use array data structure:

1. Find a pair with the given sum in an array
2. Check if a subarray with 0 sum exists or not
3. Print all subarrays with 0 sum
4. Sort binary array in linear time
5. Find maximum length subarray having a given sum
6. Find maximum length subarray having an equal number of 0’s and 1’s
7. Find the maximum product of two integers in an array
8. Sort an array of 0’s, 1’s, and 2’s (Dutch National Flag Problem)
9. In-place merge two sorted arrays
10. Merge two arrays by satisfying given constraints
11. Find the index of 0 to be replaced to get the maximum length sequence of continuous ones
12. Shuffle an array using Fisher–Yates shuffle algorithm
13. Rearrange an array with alternate high and low elements
14. Find equilibrium index of an array
15. Find the largest subarray formed by consecutive integers
16. Find majority element (Boyer–Moore Majority Vote Algorithm)
17. Move all zeros present in an array to the end
18. Replace every array element with the product of every other element
19. Longest Bitonic Subarray Problem
20. Find the maximum difference between two array elements that satisfies the given constraints
21. Print continuous subarray with maximum sum
22. Maximum Sum Circular Subarray
23. Find all distinct combinations of a given length — I
24. Find the maximum sequence of continuous 1’s formed by replacing at-most `k` zeroes by ones
25. Find minimum sum subarray of size `k`
26. Maximum Product Subarray Problem
27. Find a subarray having the given sum in an integer array
28. Find the smallest subarray length whose sum of elements is greater than `k`
29. Find the smallest window in an array sorting which will make the entire array sorted
30. Find maximum sum path involving elements of given arrays
31. Find maximum profit earned by buying and selling shares any number of times
32. Trapping Rain Water Problem
33. Find minimum platforms needed to avoid delay in the train arrival
34. Decode an array constructed from another array
35. Sort an array in one swap whose two elements are swapped
36. Find a triplet with the given sum in an array
37. Find the length of the longest continuous sequence with the same sum in given binary arrays
38. Reverse every consecutive `m`-elements of a subarray
39. Maximum Product Subset Problem
40. Find pairs with difference `k` in an array
41. 4–Sum Problem | Quadruplets with a given sum
42. Print all quadruplets with a given sum | 4 sum problem extended
43. Quickselect Algorithm
44. Rearrange array such that `A[A[i]]` is set to `i` for every element `A[i]`
45. Print all triplets that form an arithmetic progression
46. Print all triplets that form a geometric progression
47. Group elements of an array based on their first occurrence
48. Find the minimum difference between the index of two given elements present in an array
49. Find the maximum absolute difference between the sum of two non-overlapping subarrays
50. Find all symmetric pairs in an array of pairs
51. Find the closest pair to a given sum in two sorted arrays
52. Partition an array into two subarrays with the same sum
53. Find the count of distinct elements in every subarray of size `k`
54. Find two numbers with maximum sum formed by array digits
55. Print all subarrays of an array having distinct elements
56. Find a triplet having the maximum product in an array
57. Find the minimum index of a repeating element in an array
58. Find a pair with a minimum absolute sum in an array
59. Find an index of the maximum occurring element with equal probability
60. Check if an array is formed by consecutive integers
61. Find two non-overlapping pairs having the same sum in an array
62. Add elements of two arrays into a new array
63. Find minimum product among all combinations of triplets in an array
64. Count distinct absolute values in a sorted array
65. Print all combinations of positive integers in increasing order that sums to a given number
66. Find all distinct combinations of a given length — II
67. Find subarrays with a given sum in an array
68. Find maximum length sequence of continuous ones (Using Sliding Window)
69. Find maximum length sequence of continuous ones
70. Find the index that divides an array into two non-empty subarrays with equal sum
71. Efficiently calculate the frequency of all elements present in a limited range array
72. Rearrange an array such that it contains positive and negative numbers at alternate positions
73. Find the sorted triplet in an array
74. Shuffle an array according to the given order of elements
75. Count the number of strictly increasing subarrays in an array
76. Find duplicates within a range `k` in an array
77. Find a minimum range with at least one element from each of the given arrays
78. Find the longest subsequence formed by consecutive integers
79. Determine the index of an element that satisfies given constraints in an array
80. Find minimum moves required for converting a given array to an array of zeroes
81. Left rotate an array
82. Right rotate an array `k` times
83. Activity Selection Problem
84. Job Sequencing Problem with Deadlines
85. 3–partition problem extended | Printing all partitions
86. Count triplets which form an inversion in an array
87. Determine whether an array can be divided into pairs with a sum divisible by `k`
88. Find minimum removals required in an array to satisfy given constraints
89. Find a pair with the given sum in a circularly sorted array
90. Segregate positive and negative integers in linear time
91. Find the minimum and maximum element in an array using minimum comparisons
92. Insertion Sort Algorithm
93. Selection Sort Algorithm
94. Bubble Sort Algorithm
95. Merge Sort Algorithm
96. Iterative Merge Sort Algorithm (Bottom-up Merge Sort)
97. Quicksort Algorithm
98. Hybrid QuickSort Algorithm
99. Quicksort using Dutch National Flag Algorithm
100. Quicksort algorithm using Hoare’s partitioning scheme
101. Counting Sort Algorithm
102. Heap Sort Algorithm
103. Introsort Algorithm — Overview and C++ Implementation
104. External Merge Sort Algorithm
105. Inversion count of an array
106. Problems solved using partitioning logic of Quicksort
107. Sort elements by their frequency and index
108. Sort an array based on order defined by another array
109. Efficiently sort an array with many duplicated values
110. Find the largest number possible from a given set of numbers
111. Find surpasser count for each array element
112. Segregate positive and negative integers using merge sort
113. Water Jugs Problem
114. Sort an array using Young tableau
115. Find all combinations of elements satisfying given constraints
116. K–Partition Problem | Printing all partitions
117. Find all distinct combinations of a given length with repetition allowed
118. Print all combinations of numbers from 1 to `n` having sum `n`
119. Print all triplets in an array with a sum less than or equal to a given number
120. Difference between Subarray, Subsequence, and Subset
121. Print all distinct subsets of a given set
122. Find the missing number in an array
123. Find the missing number in an array without using any extra space
124. Find the odd occurring element in an array in a single traversal
125. Find two odd occurring elements in an array without using any extra space
126. Find all odd occurring elements in an array having a limited range of elements
127. Find the duplicate element in a limited range array
128. Find two duplicate elements in a limited range array (using XOR)
129. Find the missing number and duplicate elements in an array
130. Merging Overlapping Intervals
131. Maximum Overlapping Intervals Problem
132. Find the next greater element for every element in a circular array
133. Find the next greater element for every array element
134. Find the previous smaller element for each array element
135. Reverse an array in C++
136. Longest Increasing Subsequence Problem
137. Find all elements in an array that are greater than all elements to their right
138. Iterative Implementation of Quicksort
139. Combinations of words formed by replacing given numbers with corresponding alphabets
140. Replace every array element with the least greater element on its right
141. Print complete Binary Search Tree (BST) in increasing order
142. Binary Search Algorithm
143. Find the number of rotations in a circularly sorted array
144. Search an element in a circularly sorted array
145. Find the first or last occurrence of a given number in a sorted array
146. Count occurrences of a number in a sorted array with duplicates
147. Find the smallest missing element from a sorted array
148. Find floor and ceil of a number in a sorted integer array
149. Search in a nearly sorted array in logarithmic time
150. Find the number of 1’s in a sorted binary array
151. Find the peak element in an array
152. Maximum Subarray Sum using Divide and Conquer
153. Find the missing term in a sequence in logarithmic time
154. Find floor and ceil of a number in a sorted array (Recursive solution)
155. Find the frequency of each element in a sorted array containing duplicates
156. Find the odd occurring element in an array in logarithmic time
157. Find pairs with difference `k` in an array | Constant Space Solution
158. Find `k` closest elements to a given value in an array
159. Find the minimum and maximum element in an array using Divide and Conquer
160. Binary Search in C++ STL and Java Collections
161. Ternary Search vs Binary search
162. Exponential search
163. Interpolation search
164. Longest Increasing Subsequence using Dynamic Programming
165. Longest Decreasing Subsequence Problem
166. Longest Bitonic Subsequence
167. Maximum Sum Increasing Subsequence Problem
168. Matrix Chain Multiplication using Dynamic Programming
169. 0–1 Knapsack Problem
170. Maximize the value of an expression
171. Partition Problem using Dynamic Programming
172. Subset Sum Problem — Dynamic Programming Solution
173. 3–Partition Problem
174. Minimum Sum Partition Problem
175. Rod Cutting Problem
176. Coin change-making problem
177. Coin Change Problem
178. Longest Alternating Subsequence Problem
179. Weighted Interval Scheduling Problem
180. Box Stacking Problem
181. Activity Selection Problem using Dynamic Programming
182. Weighted Interval Scheduling — Dynamic Programming Solution
183. Find minimum jumps required to reach the destination
184. Find maximum profit earned from at most `k` stock transactions
185. Find the maximum sum of a subsequence with no adjacent elements
186. Minimum-weight triangulation of a convex polygon
187. Find maximum profit that can be earned by conditionally selling stocks
188. Truncate an integer array such that `2×min` becomes more than `max`
189. Maximum Sum Subarray Problem (Kadane’s Algorithm)
190. Longest Alternating Subarray Problem
191. Find maximum profit earned from at most two stock transactions
192. Find ways to calculate a target from elements of the specified array
193. Find itinerary from the given list of departure and arrival airports
194. Introduction to Priority Queues using Binary Heaps
195. Check if an array represents a min-heap or not
196. Convert max heap to min heap in linear time
197. Find k’th largest element in an array
198. Sort a k-sorted array
199. Merge `M` sorted lists of variable length
200. Find k’th smallest element in an array
201. Find the smallest range with at least one element from each of the given lists
202. Merge `M` sorted lists each containing `N` elements
203. Connect `n` ropes with minimal cost
204. Replace each array element by its corresponding rank
205. Generate the power set of a given set
206. Set both elements of a binary array to 0 in a single line
207. Generate random input from an array according to given probabilities

Thanks for reading.