PLEASE FILE AN ISSUE IN CASE OF A BUG OR ADD A COMMENT. Feel free to email me: techpanja@gmail.com with issues or new problems.

I have a cloned repo https://github.com/techpanja/interviewproblemspublic which is open for contribution. Feel free to email me if you want to be a contributor.

A COMPILATION OF COMMON INTERVIEW QUESTIONS AND SOLUTIONS.

Sections:---

Arrays

1. Given +ve numbers in an array.Put the even #s to the left of the array and the odd to the right side of the array . Don't use extra array. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/allevennumberstoleft/AllEvensToLeftandOddsToRight.java

2. Given a sequence of non-negative integers find a subsequence of length 3 having maximum product with the numbers of the subsequence being in ascending order. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/ascsubsequencemaxproduct/SubsequenceProduct.java

3. Shift array of integers circularly given input array and shift size. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/circularshiftintarray/CircularShiftArray.java

4. Check if a sub-array exists in parent array. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/findarray/FindArrayImpl.java

5. Find duplicates count in sorted array. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/findduplicatecountsortedarray/DuplicatesCountInSortedArray.java

6. Write a program takes array input{1,0,2,3} and num = 3 and provides output {1,2}{0,3}{2,1}{3,0} sum equals the num. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/findpairsequaltosum/FindPairsEqualToSum.java

7. Find the contiguous subarray which has the largest sum. Kadane's algorithm. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/maxsubarray/FindMaxSubArray.java

8. Given two sorted (ascending) arrays of integers, find the minimum difference between two integers in that array. Link:

9. Print numbers with frequency. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/numberfrequency/PrintNumbersWithFrequency.java

10. Find Number with Highest frequency in sorted array. Link: https://github.com/techpanja/interviewproblems/blob/master/src/arrays/numberwithhighestfreq/FindNumberWithHighestFreq.java

Collections

1. Find cartesian of lists. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/cartesianproblem/CartesianOfLists.java

2. Find the common elements accross sorted sets/lists. Link:

3. Implement custom linked list. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/customlinkedlist/LinkedListImpl.java

4. Check if a linked list has loops. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/customlinkedlist/LinkedListImpl.java

5. Find nth element from end of the linked list. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/findNTHlastelement/FindNthLastElement.java

6. Find the loop starting point in a LinkedList if it contains loop. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/customlinkedlist/LinkedListImpl.java

7. Flatten a nested list. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/nestedliststring/NestedList.java

8. Given a nested list of integers, returns the sum of all integers in the list weighted by their depth. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/nestedlistsum/NestedListSum.java

9. Remove duplicate links from LinkedList. Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/removeduplicatesfromlinkedlist/RemoveDuplicatesFromLinkedList.java

10. Reverse a linked list. (In-place and using stack.) Link: https://github.com/techpanja/interviewproblems/blob/master/src/collections/customlinkedlist/LinkedListImpl.java

Iterator

1. Implement custom iterator. Link: https://github.com/techpanja/interviewproblems/blob/master/src/customiterator/AnimalIterator.java

Graphs

1. Breadth First Search Link: https://github.com/techpanja/interviewproblems/blob/master/src/graphs/breadthfirstsearch/BFS.java

2. Depth First Search Link:

3. File Dependency Resolution Link: https://github.com/techpanja/interviewproblems/blob/master/src/graphs/graph/AbstractGraph.java

Heaps

1. Max Heaps Link: https://github.com/techpanja/interviewproblems/blob/master/src/heaps/heap/MaxHeap.java

2. Min Heaps Link: https://github.com/techpanja/interviewproblems/blob/master/src/heaps/heap/MinHeap.java

Maps

1. Custom HashMap implementation. Link: https://github.com/techpanja/interviewproblems/blob/master/src/maps/customhashmap/CustomHashMapImpl.java

2. Least Recently Used (LRU) cache implementation. Link: https://github.com/techpanja/interviewproblems/blob/master/src/maps/lrucache/LRUCache.java

Number-Problems

1. Concatenate two numbers. for e.g. 123, 0456 = 1230456 Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/concatenatenumbers/ConcatenateNumbers.java

2. Convert string to number. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/convertstringtonumber/ConvertStringToNum.java

3. Find exponential of a number in fastest time. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/exponentialnumber/ExponentialOfNumber.java

4. Find factorial of a number. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/factorial/Factorial.java

5. Find no. of trailing zeroes in a factorial of number. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/factorial/FactorialNoOfTrailingZeroes.java

6. Find missing number in stream of numbers. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/findmissingnumber/FindMissingNumber.java

7. Check if a number is odd or even without using / % * + - operators. Link:

8. Swap Numbers. Link: https://github.com/techpanja/interviewproblems/blob/master/src/numberproblems/swapnumbers/SwapNumbers.java

Objects

1. Cloning example (Linked List). Link: https://github.com/techpanja/interviewproblems/blob/master/src/objects/cloning/linkedlistclone/LinkedListCloning.java

2. Implement an Immutable class. Link: https://github.com/techpanja/interviewproblems/blob/master/src/objects/immutableclass/ImmutableClass.java

3. Pass by value example. Link: https://github.com/techpanja/interviewproblems/blob/master/src/objects/passbyvalue/PassByValue.java

4. Implement a singleton class. (Double-check Locking and Static) Link: https://github.com/techpanja/interviewproblems/tree/master/src/objects/singleton

Sorting

1. Bubble Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/BubbleSort.java

2. Insertion Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/InsertionSort.java

3. Merge Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/MergeSort.java

4. Quick Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/QuickSort.java

5. Selection Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/SelectionSort.java

6. Shell Sort. Link: https://github.com/techpanja/interviewproblems/blob/master/src/sorting/algorithms/ShellSort.java

Stack/Queues

1. Check if opening parenthesis pattern matches closing parenthesis pattern. Link:

2. Implement a queue using stack. Link: https://github.com/techpanja/interviewproblems/blob/master/src/stackqueues/queueusingstack/QueueUsingStack.java

3. Sort a stack using only one additional stack and no other data structure. Link:

Strings

1. Check string palindrome. Link:

2. Find common prefix for a given list of strings. Link:

3. Find duplicate strings in list of strings. Link:

4. Find latest version problem. Link:

5. Find Longest Common Subsequence. Link:

6. Find Longest Palindrome in a string. Link:

7. Print permutations of all characters in a string. Link:

8. Find total number of palindromes in a String. Link:

9. Find first non-repeated character. Link:

10. Given two (dictionary) words as Strings, determine if they are isomorphic. Link:

11. Given s string, Find max size of a sub-string, in which no duplicate chars present. Link:

12. Find min substring that contains all the char of target string. Link:

13. Print diamonds on basis of input size. Link:

14. Identify all the 'n' (n will be input) letter-long sequences that occur more than once in any given input string. OR Find repeating sequence of specified length in given DNA chromosome sequence. Link:

15. Reverse a string. Link:

16. Find all dictionary words in a given string. Link:

17. Return true if stringA is subsequence of stringB. Link:

18. Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 using only one call to isSubstring. Link:

19. Check if a string has all unqiue characters. Link:

20. Count word occurrence in a large text file. Link:

Threads

1. Implement blocking queue. Link: https://github.com/techpanja/interviewproblems/blob/master/src/threads/blockingqueue/BlockingQueue.java

2. Simulate a deadlock. Link: https://github.com/techpanja/interviewproblems/blob/master/src/threads/simulatedeadlock/DeadLockOreilly.java

Trees

1. Check Balanced Tree. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/checkbalancedtree/CheckBalancedTree.java

2. Check if a tree is Subtree of parent tree. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/checksubtree/CheckSubtree.java

3. Find common ancestor of two nodes in a binary tree (not necessarily BST). Link:

4. Find diameter Of Tree. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/diameteroftree/DiameterOfTree.java

5. Find All Paths Equal To Sum. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/findallpathsequaltosum/FindAllPathsEqualToSum.java

6. Find Sum Of All Nodes Except Leaf. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/findsumofallnodesexceptleaf/FindSumOfAllNodesExceptLeaf.java

7. Check is a given tree is binary search tree. (recursive and non recursive) Link:

8. Find least common ancestor (LCA) of a binary search tree given two nodes. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/leastcommonancestorbst/FindLeastCommonAncestorBST.java

9. Left View of a Tree. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/leftviewofatree/LeftViewOfATree.java

10. Mirror Given Tree. Link:

11. Check if a tree is Mirror of another Tree. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/mirrortree/MirrorTree.java

12. Print Nary Tree With Levels. Link: https://github.com/techpanja/interviewproblems/blob/master/src/trees/printnarytreewithlevels/PrintNaryTreeWithLevels.java

13. Given a sorted array, create a balanced tree. Link:

*** NOTE: Some problems might be in-complete. I have added TODO for such problems. ***