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A covering graph is a subgraph which contains either all the vertices or all the edges corresponding to some other graph. A subgraph which contains all the vertices is called a line/edge covering. A subgraph which contains all the edges is called a vertex covering. Line Covering Let G = (V, E) be a graph. A subset C(E) is called a line covering of G if every vertex of G is incident with at least one edge in C, i.e., deg(V) ≥ 1 ∀ V ∈ G Because each vertex is connected with another vertex by ... Read More
Trees are graphs that do not contain even a single cycle. They represent hierarchical structure in a graphical form. Trees belong to the simplest class of graphs. Despite their simplicity, they have a rich structure. Trees provide a range of useful applications as simple as a family tree to as complex as trees in data structures of computer science. Tree A connected acyclic graph is called a tree. In other words, a connected graph with no cycles is called a tree. The edges of a tree are known as branches. Elements of trees are called their ... Read More
A Java List can be created in multiple ways depending on whether you need a modifiable list, a fixed-size list, or want to initialize it with values in a single statement. Way 1: Raw Type (Not Recommended) Create a List without specifying the type of elements. The compiler will show an unchecked warning − List list = new ArrayList(); Way 2: Generic Type (Recommended) Create a List with a specified element type for type safety − List list = new ArrayList(); Way 3: Initialize in One Line Create ... Read More
The addAll() method of the List interface can be used to combine two lists in Java. It comes in two variants − one appends elements at the end, and another inserts elements at a specific index. addAll() Without Index Appends all elements from the specified collection to the end of the list − boolean addAll(Collection
Java Streams (Java 8+) can be used to search for an item within a list by filtering elements based on a condition. The filter() method applies the search criteria, and findAny() returns the first matching element or null if no match is found. Syntax Student result = list.stream() .filter(s -> s.getRollNo() == rollNo) .findAny() .orElse(null); This filters the list for a student with the matching roll number. findAny() returns an Optional, and orElse(null) returns null if no match is found. Example ... Read More
A Java List can be converted to a Set to eliminate duplicate entries. The resulting Set will contain only unique values. There are three common ways to perform this conversion − Method 1: Using Set Constructor Pass the list directly to the HashSet constructor − Set set = new HashSet(list); Method 2: Using addAll() Create an empty set and use addAll() to add all elements from the list − Set set = new HashSet(); set.addAll(list); Method 3: Using Streams (Java 8+) Use the Stream API to collect list ... Read More
A List of elements can be copied to another List in Java using multiple approaches. All methods create a shallow copy − the new list contains references to the same objects as the original. Way 1: Constructor Pass the source list to the ArrayList constructor − List copy = new ArrayList(list); Way 2: addAll() Create an empty list and use addAll() to add all elements from the source − List copy = new ArrayList(); copy.addAll(list); Way 3: Collections.copy() Use Collections.copy() to copy elements into an existing destination list. ... Read More
Yes, Java allows easy conversion between List and Set using their constructors. Converting a List to a Set eliminates duplicate entries, and converting a Set back to a List gives a list with only unique values. List to Set Pass the list to the HashSet constructor. Duplicates are automatically removed − Set set = new HashSet(list); Set to List Pass the set to the ArrayList constructor to get a modifiable list − List list = new ArrayList(set); Example The following example demonstrates converting a List to a Set ... Read More
Yes, Java provides built-in methods to convert between arrays and lists. Use Arrays.asList() to convert an array to a list, and list.toArray() to convert a list back to an array. Array to List Use Arrays.asList() to convert an array into a list. Wrap it in an ArrayList constructor to get a modifiable list − List list = new ArrayList(Arrays.asList(array)); List to Array The List interface provides two toArray() methods − 1. Without parameter − Returns an Object[] array. Object[] items = list.toArray(); 2. With typed array − Returns ... Read More
A Java List can be converted to a Set to eliminate duplicate entries. The resulting Set will contain only unique values. There are three common ways to perform this conversion − Method 1: Using Set Constructor Pass the list directly to the HashSet constructor − Set set = new HashSet(list); Method 2: Using addAll() Create an empty set and use addAll() to add all elements from the list − Set set = new HashSet(); set.addAll(list); Method 3: Using Streams (Java 8+) Use the Stream API to collect list ... Read More