**What are Java coding questions?**

The Java coding problems include questions in data structures or algorithms, such as arrays, strings, linked lists, binary trees, maps, stacks and queues, graphs, sorting, recursions, math and numbers, files, and system designs.

### Table of Content

- Java coding problems
- The implementation of data structures
- Java Collections APIs
- Java coding interview book PDF
- The format of the book
- Source code included

Java coding problems

**Part I Data Structures and APIs**

1 Arrays

2 Strings

3 Linked Lists

4 Binary Trees

5 Hashing and Priority Queues

6 Stacks and Queues

7 Graphs

8 Matrices

9 Tries and Nary Trees

10 Intervals and Points

**Part II Algorithms and Designs**

11 Sorting and Binary Search

12 Recursion

13 Dynamic Programming

14 Numbers and Bits

15 Files, Streams, and Iterators

16 System Designs

**Part I Data Structures and APIs**

**1 Arrays**

1.1 Find max

1.2 Find min and max in one pass

1.3 Find top two in one pass

1.4 Find majority elements

1.5 Move all zeros to end

1.6 Find duplicate and missing

1.7 Find duplicate number

1.8 Remove duplicates in place

1.9 Find intersection of two sorted arrays

1.10 Merge two sorted arrays

1.11 Reverse array

1.12 Rotate array

1.13 Next permutation

1.14 Two sum

1.15 Three sum

1.16 Subarray sum to K

1.17 Max sum of subarray

1.18 Max sum of subarray size K

1.19 Max product of subarray

1.20 Self exclude product

1.21 Max profit selling stocks

1.22 Jump game

1.23 Task scheduler

1.24 Trap rain water

1.25 Trap most water

1.26 Max rectangle in histogram

**2 Strings**

2.1 Reverse string

2.2 Reverse words

2.3 Rotate string

2.4 Find first unique character

2.5 Find repeated substring size K

2.6 Find all subset words

2.7 Ransom note

2.8 Run length encoding

2.9 Swap even odd

2.10 Is anagram

2.11 Find anagram substring indices

2.12 Group anagrams

2.13 Is isomorphic

2.14 Is palindrome

2.15 Longest palindromic substring

2.16 Longest substring with unique chars

2.17 Longest common prefix

2.18 Min window substring

2.19 Min insertions to form palindrome

2.20 Shortest subarray contains all words

2.21 Word wrap

2.22 Word break

2.23 Word ladder

**3 Linked Lists**

3.1 Find node

3.2 Detect loop

3.3 Delete node

3.4 Delete every Kth node in DLL

3.5 Last men standing

3.6 Print from end

3.7 Reverse linked list

3.8 Reverse K nodes

3.9 Is palindrome

3.10 Find intersection of two lists

3.11 Merge two sorted lists

3.12 Merge K sorted lists

3.13 Sort linked list

3.14 Interleave list

3.15 Flatten doubly linked list

3.16 Add two numbers

3.17 Deep copy random pointers

**4 Binary Trees**

4.1 Get height

4.2 Get diameter

4.3 Is balanced

4.4 Is BST

4.5 Is complete

4.6 Is subtree

4.7 Is symmetric

4.8 Flip tree

4.9 Find lowest common ancestor

4.10 Find distance of two nodes

4.11 Find in-order successor in BST

4.12 Find Kth largest in BST

4.13 Populate next pointers to right nodes

4.14 Binary tree traversal iteratively

4.15 Level order

4.16 Print vertical

4.17 Print side view

4.18 Print leaves

4.19 Print all root to leaf paths

4.20 Path sum to K

4.21 Max path sum

4.22 Sum of nodes

4.23 Convert sorted array to BST

4.24 Convert sorted linked list to BST

4.25 Convert Binary tree to doubly linked list

4.26 Serialize and deserialize

**5 Hashing and Priority Queues**

5.1 Object as key

5.2 Remove duplicate contacts

5.3 Get all element counts

5.4 Sort pairs

5.5 Find most popular cost books

5.6 Find year with most population

5.7 Find X to make array sum to K

5.8 Find Kth largest

5.9 Find top K frequent elements

5.10 Find K closest to center

5.11 Find top K tweet words in last hour

**6 Stacks and Queues**

6.1 Implement stack with queues

6.2 Implement stack with min()

6.3 Validate parentheses

6.4 Infix to postfix

6.5 Prefix to postfix

6.6 Calculate postfix

6.7 Calculate infix

6.8 Implement queue with stacks

6.9 Implement queue with max()

6.10 Remove invalid parentheses

6.11 Find max in sliding window

6.12 Find moving average in sliding window

**7 Graphs**

7.1 Graph traversal

7.2 Clone graph

7.3 Detect cycle

7.4 Find degree of vertex

7.5 Is bipartite

7.6 Has path from source to destination

7.7 Print all paths from sources to destination

7.8 Find shortest path with BFS

7.9 Find shortest path with Dijkstra’s

7.10 Topological sort with DFS

7.11 Courses order

**8 Matrices**

8.1 Search in sorted matrix

8.2 Rotate matrix by 90 degrees

8.3 Print matrix in spiral Order

8.4 Fill rows and columns with 1s

8.5 Min distance of meeting point

8.6 Number of islands

8.7 Find path between cells

8.8 Word search on board

8.9 Max region

8.10 Longest increasing path

8.11 Find shortest path between cells

8.12 Nearest bikes

**9 Tries and Nary Trees**

9.1 Implement trie methods

9.2 Autocomplete

9.3 Find distinct palindromic substrings

9.4 Longest repeated substring

9.5 Get height

9.6 Get diameter

9.7 Find lowest common ancestor

9.8 Find distance of two nodes

9.9 Nary tree traversal iteratively

9.10 Level order

9.11 Build hierarchy tree

9.12 Monarchy succession order

**10 Intervals and Points**

10.1 Merge intervals

10.2 Insert interval

10.3 Count intervals range

10.4 Schedule meetings

10.5 Weighted job scheduler

10.6 Is overlapped

10.7 Is square

10.8 Draw skyline

10.9 Distance of nearest stores

**Part II Algorithms and Applications**

**11 Sorting and Binary Search**

11.1 Bubble sort

11.2 Selection sort

11.3 Insertion sort

11.4 Merge sort

11.5 Quick sort

11.6 Find Kth largest and smallest

11.7 Sort squares

11.8 Binary search in sorted array

11.9 Binary search in rotated sorted array

11.10 Find occurrences in sorted array

11.11 Find peak element

11.12 Find first larger than K

11.13 Find largest smaller than K

11.14 Find missing in consecutive numbers

11.15 Find missing in arithmetic progression

**12 Recursion**

12.1 Permutation of array

12.2 Permutation of string

12.3 Generate binary strings

12.4 Generate valid parentheses

12.5 Generate strobogrammatic numbers

12.6 Permutation of multiple arrays

12.7 All subsets of an array

12.8 Combination of numbers

12.9 Combination of subset strings

12.10 Combination sum to K

12.11 Nested integers depth sum

12.12 Letter combinations of phone keypad

12.13 Partition numbers to form IP addresses

12.14 Decode numbers

12.15 Operator combinations results

**13 Dynamic Programming**

13.1 Climb stairs

13.2 Coin change

13.3 Number of ways decoding base 26

13.4 Least square numbers sum to K

13.5 Knapsack

13.6 Edit distance

13.7 Number of distinct subsequence

13.8 Longest increasing subsequence

13.9 Longest common subsequence

13.10 Longest palindromic subsequence

13.11 Number of unique paths in matrix

13.12 Min path sum in matrix

13.13 Max square area

13.14 Range sum query in matrix

13.15 Max rectangle sum in matrix

**14 Numbers and Bits**

14.1 Prime number

14.2 Random number

14.3 Random number not in array

14.4 Factorial number

14.5 Fibonacci number

14.6 Fizzbuzz

14.7 Power two

14.8 Power X of Y

14.9 Log two

14.10 Square root

14.11 Is binary

14.12 Is odd number

14.13 Reverse number

14.14 Sum of digits

14.15 Is palindromic number

14.16 Is strobogrammatic number

14.17 Add binary

14.18 Add two big string numbers

14.19 Multiply string numbers

14.20 convert string to integer

14.21 Convert decimal to base N

14.22 Base 26 encoding

14.23 Convert integer to roman numeral

14.24 Count set bits in number

14.25 Hamming distance

14.26 Find missing number

14.27 Find single number

**15 Files, Streams, and Iterators**

15.1 Count words in file

15.2 Reverse content of file in place

15.3 Clean directories recursively

15.4 Find files size larger than 5M

15.5 Add spaces around parentheses in code

15.6 Find Kth largest in stream

15.7 Find median in stream

15.8 Merge K sorted streams in one

15.9 Check palindrome in stream

15.10 Binary tree in-order iterator

15.11 File line iterator

15.12 Rate limiter iterator

**16 System Designs**

16.1 Dictionary and spell checker

16.2 Phone directory

16.3 Log analyzer

16.4 Tiny url

16.5 Version control snapshot

16.6 Load balancer

16.7 LRU cache

The implementation of data structures

**Arrays**

Array implementation

Sorted array implementation

**Linked Lists**

Singly linked list implementation

Doubly linked list implementation

Circular linked list implementation

**Binary Trees**

Binary tree implementation

Binary search tree implementation

**Hashing and Priority Queues**

Hash function and hash table implementation

Priority queue implementation with array

**Stacks and Queues**

Stack implementation with Array

Stack implementation with linked list

Queue implementation with linked list

Circular Queue implementation with array

**Graphs**

Graph implementation

**Tries and Nary Trees**

Trie implementation

Suffix trie implementation

Nary tree implementation

Java Collections APIs and their methods

ArrayList APIs

String APIs

Regex APIs

LinkedList APIs

HashMap APIs

HashSet APIs

Hashtable APIs

PriorityQueue APIs

Stack APIs

Queue APIs

Deque APIs

Convert APIs

BigInteger APIs

Date time APIs

Bitwise and Bitshift

File APIs

FileReader and FileWriter APIs

FileInputStream and FileOutputStream APIs

Scanner APIs

Java coding interview book

Java coding interview book compiles most asked (up to 250) Java coding interview questions and answers. It not only answers the basic must-known questions, such as sorting or file reading, but also includes the hard and even tricky questions from companies such as Google, Amazon.

Java coding interview book

$7.98

The format of the book

Besides the coverage, the book insight explains how we format the book. The current edition (2nd edition) of the book has PDF and ePub format. The PDF uses “Complete-Code-In-One-Page” format. The question and the code display on one page, not across over to the next page. This format makes it easy to read and compare the similarity between questions. Here are the examples:

The ePub format shows one function per page. It is perfect to be used as a pocket book. You can use it anytime, anywhere on the go.

Source code included

The book comes with the source code. The source code provides the full question statement, sample input, and output. It also has an explanation of Big O notations. Sometimes, alternative solutions are available for follow-up questions. Make sure to study them along with the book.