♦ Tree – Get root to leaf max sum in Java example

Q. Write code to traverse a tree and get the largest “root-to-leaf sum”? A “root-to-leaf sum” is a sum of the node values in a root-to-leaf path. A. Let’s have a basic implementation of the above Node interface. Here is…...

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♦ Tree traversal algorithms in Java

Q1. What are the different binary tree traversal mechanisms? A1. Traversing a tree means visiting all the nodes of a tree in order. Many different binary tree algorithms involve traversals. For example, if you wish to count the number of…...

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♥ Beginner array coding problems in Java

More Data Structure and Algorithms Coding Questions and answers in Java. Q1. Write a program that allows you to create an integer array of 5 elements with the following values: int numbers[ ]={5,2,4,3,1}. The program computes the sum of first

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♥ Big O notation questions and answers

Q1. What do you know about the big-O notation and can you give some examples with respect to different data structures? A1. The Big-O notation simply describes how well an algorithm scales or performs in the worst case scenario as

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♦ Find 2 numbers from an array that add up to the target

Q1. Given an array of integers, find two numbers such that they add up to a specific target number? For example, Given numbers: {2, 3, 8, 7, 5} Target number: 9 Result: 2 and 7 A1. Solution 1: Store processed…...

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♦ Is it a valid binary search tree (BST) ?

Q. Write code test if a given tree is a binary search tree (i.e. BST)? A. A binary search tree (BST) is a binary tree where each node satisfies the following conditions: 1) key in any node is larger than…...

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♦ Tree – Sum Levels Java example

Q. Write code to traverse a tree and return the sum of the values (Node.getValue()) of all nodes at the level N in the tree? A. Let’s have a basic implementation of the above Node interface. Here is the getLevelSum(root,…...

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03: Understanding Big O notations through Java examples

Q. Have you seen job advertisements requiring Java candidates to work in real-time or high volume transaction processing systems? If you are applying for such jobs, you can be quizzed on Big O notation. Here are some basics to brush up on. Big-O gives…...

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09: ♦ When to use which Java data structure? and why?

List, Set, Map, and Queue(access the ends FIFO or LIFO) are the basic Java data structure interfaces for which there are different implementations to cater for different usage patterns. Java data structure interview questions are very popular, and pays to…...

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9 Java Data structures best practices

#1: Choose the right type of Java data structure based on usage patterns like fixed size or required to grow, duplicates allowed or not, ordering is required to be maintained or not, traversal is forward only or bi-directional, inserts at

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Binary Tree – Sum Levels Java Example

Q. Write code to traverse a tree and return the sum of the values (Node.getValue()) of all nodes at the level N in the binary tree? A. Let’s have a basic implementation of the above Node interface. Here is the…...

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Binary Tree – Get root to leaf max sum in Java example

Q. Write code to traverse a binary tree and get the largest “root-to-leaf sum”? A “root-to-leaf sum” is a sum of the node values in a root-to-leaf path. A. Let’s have a basic implementation of the above binary tree Node…...

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Find middle element of a LinkedList in one pass Java example

The SinglyLinkedList was created in the post “LinkedList creating from scratch in Java“. This extends “SinglyLinkedList” post. Q. How to find the middle node of a linked list in a single pass? A. Output:...

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Find pair of numbers with a given sum in Java

Q. Write a method which takes the parameters (int[ ] inputNumbers, int sum) and checks input to find the pair of integer values which totals to the sum. If found returns true, else returns false? Considerations: Should it work for…...

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Graph from scratch Java example

Q. Java does not have a Graph implementation, how would you go about implementing your own? A. Graphs are data structures that represent arbitrary relationships between members of any data sets that can be represented as networks of nodes and…...

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Graph from scratch Java example adjacent matrix approach

Q. Java does not have a Graph implementation, how would you go about implementing your own? A. Graphs are data structures that represent arbitrary relationships between members of any data sets that can be represented as networks of nodes and…...

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HashMap from scratch Java example

Q. If Java did not have a HashMap implementation, how would you go about writing your own one? A. Writing a HashMap is not a trivial task. It is also not a good practice to reinvent the wheel. The interviewer…...

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Linear & Binary Search in Java

Q. Can you write a code to search for number 5 in 7 3 6 8 2 9 5 4? A. The code below uses the linear search algorithm. The linear search algorithm’s two advantages are simplicity and the ability…...

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LinkedList creating from scratch in Java

Q. How to create a LinkedList from scratch A. Adding Removing Step 1: The node that stores the data and the reference to the next Node. Step 2: The LinkedList with add and remove logic. Removing has 4 possible scenarios…...

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Part 2: Java Tree structure interview questions and coding questions

In the previous post entitled  Java Tree structure interview questions and coding questions — Part 1, we looked at a very simple Tree structure. In this example, let’s look at a more complex tree structure with generics. Q. Write classes…...

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Part 4: Java Tree structure interview and coding questions

This is an extension to Java Tree structure interview questions and coding questions — Part 3 where recursion was used for FlattenTree interface. Let’s use iteration here. Step 1: The FlattenTree  interface. Step 2: The iterative implementation IterativeFlattenTree. This uses a LIFO stack to…...

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Part-1: Basic Java Tree structure interview questions and coding questions

Java does not have a Tree class but you can define one. In my 10+ years as a Java developer, I have rarely used a Tree structure,  but when I do use it I find it to be a bit…...

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Part-3: Java Tree structure interview and coding questions

This is an extension to Java Tree structure interview and coding questions — Part 2, and adds functional programming and recursion. Step 1: The Tree interface with get( ) method that returns either a Triple tree or Leaf data. Step 2:…...

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Queue from scratch Java example

Q. If Java did not have a Queue implementation, how would you go about implementing your own? A. A queue can be implemented in a similar fashion to a stack by declaring a backingArray, a frontIndex, a backIndex, and a…...

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Quick Sort in Java

Q. Is there a more efficient sorting algorithm than bubble sorting? A. Although bubble-sort is one of the simplest sorting algorithms, it’s also one of the slowest. It has the O(n2) time complexity. Faster algorithms include quick-sort and heap-sort. The…...

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Single Pointer: Partitioning around a pivotal number

Q. How will you partition the following numbers 7 3 6 8 2 9 5 4 around the pivotal number of 5 so that the lower values are in front of it and higher values are behind it? A. A…...

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Sorting by reversing the entries in Java

Q. You need to sort an array of integers by repeatedly reversing the order of the first several elements of it. you always have to flip from the beginning element, you cannot flip elements 2 and 3. For example, input:…...

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Stack from scratch Java example

Q. If Java did not have a Stack implementation, how would you go about implementing your own? A. Determine the backing data structure (e.g. array, linked list, etc). Determine the methods that need to be implemented like pop( ), push(…...

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Swap 2 values & bubble sort in Java

Q1. Can you write an algorithm to swap two values? A1. Swapping without a temp variable Note: also try with * and \ Using bitwise “xor” Q2. Can you write code to bubble sort { 30, 12, 18, 0, -5,…...

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Swapping, partitioning, and sorting algorithms in Java

Q1. Can you write an algorithm in Java to swap two variables? A1. Q2. Can you write an algorithm to bubble sort the following array { 30, 12, 18, 0, -5, 72, 424 }?? A2. Q3. Is there a more…...

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Tree flattening example in Java

Q. Traverse the tree in depth and return a list of all passed nodes. It should handle different data types as Double, String, etc. The4 interface for the tree node is A. Tree storing numbers: Tree storing text: #1. Define…...

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Tree structure – calculate average recursively & iteratively in Java

Q. Complete the following “TreeProcessingImpl” class ….. so that the unit tests shown below pass? Skeleton Code Unit Tests A. Solution 1: Solution 2: Using recursion for getAverage(…) and iteration for getSum(…) Key Points #1: Recursion can cause stack overflow…...

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Two Pointers: Partitioning around a pivotal number

Q. How will you partition the following numbers 7 3 6 8 2 9 5 4 around the pivotal number of 5 so that the lower values are in front of it and higher values are behind it? The pointers…...

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