Important Coding Questions for Technical Interview

So, I’ve been coding for my placement preparations from my B.E. days on many websites. I prepared a list of the coding questions which I found important.

1. Special Numbers
2. Count complete tree nodes
3. Convert a Ternary expression to a Binary tree structure?
   GFG’s Java solution is wrong. C++ solution is correct.
4. Maximum sum subarray removing at most one element
5. Compare Version Numbers
6. Repeated Substring Pattern
7. Longest Increasing Path in a Matrix
8. Binary Search Tree (BST) — Interview Questions & Practice Problems
9. Check if given keys represents same BSTs or not without building the BST
10. Find distance between two nodes of a Binary Tree
11. Sink nodes containing zero to the bottom of a binary tree
12. Permutations
13. Number of occurrence of maximum grid
14. Minimum Number of Platforms Required for a Railway/Bus Station
15. Next Permutation
16. Longest Common Prefix
17. Find size of the largest BST in a Binary Tree
18. Consecutive 1’s not allowed
19. Decode Ways
20. Product of Array Except Self
21. Search in Rotated Sorted Array
22. Minimum sum partition
23. Two City Scheduling
24. Minimum Insertion Steps to Make a String Palindrome
25. Interleaving String
26. Triangle
27. Fixing Two nodes of a BST
28. Applications of Catalan Numbers
29. How to check whether the number is an Integer ?
30. In Java, we check if a number is an integer by taking the decimal part
    (using % 1) and checking if it is 0.
31. If floor(number)==ceil(number), it is an integer
32. Find Peak Element (See binary search solution)
33. Valid Sudoku — — See this solution
34. Find three closest elements from given three sorted arrays
35. Is Subsequence | Leetcode #392 | Binary search + Map | 2 Pointer
36. Union find method to detect cycle in graph.
37. Check if two Binary Trees are Isomorphic
38. Disjoint Sets using union by rank and path compression Graph Algorithm
39. Sum of given range | Segment tree construction and update | Simplest explanation
40. Rotate Image
41. Add Binary Strings (See Java Answer)
42. An Interesting Method to Generate Binary Numbers from 1 to n
43. Gas Station
44. https://practice.geeksforgeeks.org/tracks/md-tree/?batchId=144
45. Lowest Common Ancestor in a Binary Tree | Set 1
    Lowest Common Ancestor in a Binary Tree | Set 2 (Using Parent Pointer)
46. Expression Tree
47. Course Schedule
48. Word Ladder
49. Reverse a stack using recursion : Interview Question: Reverse Stack
50. Count number of inversions in array
51. https://practice.geeksforgeeks.org/problems/clone-a-linked-list-with-next-and-random-pointer/1/?track=sp-linked-list&batchId=152
52. Reverse Bits
53. Activity Selection
54. Egg Dropping Puzzle (Variation 1) : Solution
55. Eggs dropping puzzle | Variation 2 : Solution
56. Converting Decimal Number into Roman Numerals
57. The Painter’s Partition Problem
58. https://practice.geeksforgeeks.org/problems/allocate-minimum-number-of-pages0937/1/?track=dp-divide-and-conquer&batchId=152
59. Exponents of large numbers
60. Print all subarrays with 0 sum
61. Maximum Path Sum in a Binary Tree
62. Populating Next Right Pointers in Each Node — — 1 &&&& each-node-2
63. N-Queens
64. Reverse a Linked List in groups of given size | Set 1
65. Flattening a Linked List
66. The Stock Span Problem
67. Morris Inorder Tree Traversal
68. First Missing Positive
69. Median of Two Sorted Arrays
70. Sort a nearly sorted (or K sorted) array
71. Sliding Window Maximum (Maximum of all subarrays of size k)
72. Find median in a stream
73. Delete Nodes And Return Forest
74. Find the Missing Number
75. Find K Closest Elements : See solution
76. Box Stacking
77. Hamming Distance
78. Word Break
79. Next larger element
80. Rearrange characters in a string such that no two adjacent are same
81. Merge k Sorted Lists
82. Sequences of given length where every element is more than or equal to twice of previous
83. Modular Exponentiation (Power in Modular Arithmetic)
84. Linked List Cycle and detect starting point of the cycle
85. Rectangle Overlap : Check Comments for the solution
86. Sorting elements by frequency
87. Lowest Common Ancestor in a Binary Tree | Set 2 (Using Parent Pointer)
88. Find n-th node of inorder traversal
89. Google | Phone | Find K-th node in inorder traversal
90. Wiggle Sort II
91. Maximal Square O(n)
92. Wave Array : Check out O(n) solution
93. Count Primes : How is the time complexity of Sieve of Eratosthenes is n*log(log(n))?
    https://www.youtube.com/watch?v=pKvGYOnO9Ao
94. Possible Bipartition : Solution
95. Add Digits : See Solution
96. Edit Distance
97. Longest palindromic substring | Dynamic programming
98. How to calculate Catalan Number | Find Nth catalan number in most efficient ways (3 methods)
99. Two City Scheduling : https://leetcode.com/problems/two-city-scheduling/discuss/280173/Java-4-lines-intuitive-solution
100. All Nodes Distance K in Binary Tree
101. Kth Smallest Element in a BST : See follow up in solution
102. Reverse Words in a String : Solution
103. Check If It Is a Straight Line
104. Find the Duplicate Number : See Solution → (Video Solution)
105. How to solve DP — String? Template and 4 Steps to be followed. Dynamic Programming Patterns
106. DP for Beginners [Problems | Patterns | Sample Solutions]
107. Graph Problems For Beginners Practice [Problems and Sample Solutions]
108. Sliding Window for Beginners [Problems | Template | Sample Solutions]
109. Important and Useful links from all over the Leetcode
110. K Closest Points to Origin
111. Counting Bits
112. Longest array with equal number of zeros and ones
113. Rotting Oranges — Solution (O(n)) | Solution (O(n3))
114. Number of Islands
115. Difference between sums of odd level and even level nodes of a Binary Tree
116. Integer to English Words
117. Converting Decimal Number lying between 1 to 3999 to Roman Numerals
118. Check Completeness of a Binary Tree
119. Deepest Leaves Sum
120. Maximum Depth of N-ary Tree
121. Stone Game : See its solution (Method 2)
122. Coin Change
123. Unique Binary Search Trees
124. Count of Smaller Numbers After Self
125. Majority Element
126. Single Number II : Solution
127. https://www.youtube.com/watch?v=BXCEFAzhxGY&t=90s
128. Symmetric Tree
129. Remove Duplicates from Sorted List II
130. Largest Rectangular Area in a Histogram | Set 2
131. A program to check if a binary tree is BST or not
132. Construct BST from given preorder traversal
133. Partition Equal Subset Sum
134. Remove K Digits : Keep all edge cases in mind (There are many edge cases)
135. Shortest Unsorted Continuous Subarray
136. Must do Math for Competitive Programming
137. Sort an array of 0s, 1s and 2s (Dutch National Flag Algorithm)
138. BigInteger Class in Java
139. Print nodes at K distance from root
140. Container With Most Water
141. Print unique rows in a given boolean matrix
142. Search a 2D Matrix
143. Odd Even Linked List
144. Unique Binary Search Trees
145. https://leetcode.com/problems/insert-delete-getrandom-o1/
146. Word Search 1 & 2 [GRAPH]
147. Additive Number [DFS]
148. Unique ways to make a change from coins : See Reduced Complexity Solution
149. House Robber [Dynamic Programming]
150. Cutting Binary String (GFG) [Dynamic Programming]
151. Maximum Product Cutting [GFG]
     A Tricky Solution: If we see some examples of these problems, we can easily observe the following pattern. The maximum product can be obtained by repeatedly cutting parts of size 3 while size is greater than 4, keeping the last part as size of 2 or 3 or 4. For example, n = 10, the maximum product is obtained by 3, 3, 4. For n = 11, the maximum product is obtained by 3, 3, 3, 2.
152. Jump Game [Different type of DP]
153. Optimal Strategy for a Game | DP-31
154. Josephus Problem (Recursion, By Pattern)
155. Subsets
156. Print all possible words from phone digits
157. Java Binary Search O(lgN) : clear, easy, explained, no tricks
158. Sort Characters By Frequency
159. Stock buy and sell
160. Top K Frequent Words
161. Lowest common ancestor in Binary Tree
162. Pairwise Swap leaf nodes in a binary tree
163. Swap Nodes in Pairs
164. Broken Calculator
165. Subarray Sum Equals K
166. Add Two Numbers II
167. Preimage Size of Factorial Zeroes Function https://leetcode.com/problems/preimage-size-of-factorial-zeroes-function/discuss/117821/Four-binary-search-solutions-based-on-different-ideas
168. Remove Nth Node From End of List
169. Top K Frequent Elements : https://leetcode.com/problems/top-k-frequent-elements/
170. Group Anagrams
171. Kth Ancestor of a Tree Node
172. A program to check if a binary tree is BST or not
173. Binary Search Tree | Set 2 (Delete)
174. Maximum Width of Binary Tree
175. Extract Leaves of a Binary Tree in a Doubly Linked List
176. https://practice.geeksforgeeks.org/problems/kth-smallest-element/
177. Merge two sorted arrays with O(1) extra space
178. Replace Words
179. Merge Intervals
180. Elimination Game
181. Search a 2D Matrix II
182. Diagonal Traversal of a matrix
183. Minimum Number of Platforms Required for a Railway/Bus Station
184. Trapping Rain Water Also see space efficient solution : https://www.geeksforgeeks.org/trapping-rain-water/
185. Median of Two Sorted Arrays
186. Noble Integer (See the use of keyword continue in its solution) : Noble Integer
187. Maximum Product Subarray
188. My Calendar
189. Largest Number
190. Number of 1 Bits
191. Program to find whether a number is power of two
192. Minimum number of jumps to reach end
193. Flatten a Multilevel Doubly Linked List
194. Count number of bits to be flipped to convert A to B
195. Count Number of SubTrees having given Sum
196. Minimum XOR Value Pair
197. Equal
198. Max Distance
199. K’th smallest element in BST using O(1) Extra Space
200. K’th Smallest/Largest Element in Unsorted Array | Set 2 (Expected Linear Time) K’th Smallest/Largest Element in Unsorted Array | Set 3 (Worst Case Linear Time)
201. Jump Game — — Youtube Video Solution
202. Jump Game II
203. Multiply Strings
204. Zig-Zag traversal of Binary tree
205. Diagonal Traversal of Binary Tree
206. Vertical order traversal of binary tree — O(n) time
207. Level Order Binary Tree && N-ary Tree Traversal
208. PreOrder (log(n), log(h)), PostOrder(1 stack, 2 stacks), InOrder (Recursive and iterative)
209. Boundary Traversal of binary tree
210. Bottom view of binary tree — O(n) time
211. Top View of Binary Tree — O(n) time
212. Left View of Binary Tree — O(n) time {Recursive and Iterative}
213. Right View of Binary Tree — O(n) time {Recursive and Iterative}
214. Detect Cycle in Undirected Graph
215. Topological sort

These Documents will contain the placement information about all the companies visiting IITs, NITs, IIITs, and BITS.

Placement 2019: https://goo.gl/tn7mRx

Interview exp 2019: https://goo.gl/vpdNNG

Placement 2018: https://goo.gl/FNziKM

Placement 2017: https://goo.gl/Xs3LdG

Placement 2016: https://goo.gl/NJXvVU

Placement 2016: https://goo.gl/yDRnCF