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♦ 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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Posted in member-paid, Tree structure

♦ 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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Posted in Algorithms, member-paid, Tree structure

♥ 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

Posted in Array Structure Tagged with: ,

♥ 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

Posted in Big O notation

♦ 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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Posted in Can you write code?, Coding, member-paid, Pointer Algorithms

♦ 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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Posted in Coding, member-paid, Tree structure

♦ 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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Posted in Big O notation, Collection and Data structures, Low Latency, member-paid

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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Posted in Collection and Data structures, member-paid, Which Data Structure & WHy

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

Posted in Best Practice, Which Data Structure & WHy

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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Posted in member-paid, Tree structure

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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Posted in member-paid, Tree structure

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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Posted in LinkedList Structure, member-paid

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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Posted in Array Structure, member-paid

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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Posted in Graph Structure, member-paid

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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Posted in Graph Structure, member-paid

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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Posted in Map Structure, member-paid

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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Posted in member-paid, Searching Algorithms

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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Posted in LinkedList Structure, member-paid

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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Posted in Coding, member-paid, Tree structure

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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Posted in Coding, member-paid, Tree structure

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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Posted in Coding, member-paid, Tree structure

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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Posted in Coding, How to use Data Structures?, member-paid, Tree structure

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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Posted in member-paid, Queue Structure

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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Posted in member-paid, Sorting Algorithms

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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Posted in member-paid, Pointer Algorithms

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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Posted in member-paid, Sorting Algorithms

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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Posted in member-paid, Stack Structure

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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Posted in Coding, member-paid, Sorting Algorithms

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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Posted in Algorithms, member-paid, Sorting Algorithms

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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Posted in member-paid, Passing the unit tests, Tree structure

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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Posted in member-paid, Pointer Algorithms

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