用 Java 实现类属图
原文:https://www . geesforgeks . org/impering-generic-graph-in-Java/
先决条件: 通用类
我们也可以用它们在 Java 中为Graph编码。图类是用 Java 中的HashMap实现的。正如我们所知，HashMap 包含一个键和值，我们将节点表示为图中值中的键和它们的邻接表。
图解:一个有 5 个顶点的无向未加权图。
邻接矩阵如下:
邻接表如下:
方法:
只是在 C++中不太可能，我们在泛型类创建中使用<>来指定参数类型。
语法:创建泛型类的对象
BaseType <Type> obj = new BaseType <Type>()
注意:在参数类型中，我们不能使用像“int”、“char”或“double”这样的原语。
例
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to implement Graph
// with the help of Generics
import java.util.*;
class Graph<T> {
// We use Hashmap to store the edges in the graph
private Map<T, List<T> > map = new HashMap<>();
// This function adds a new vertex to the graph
public void addVertex(T s)
{
map.put(s, new LinkedList<T>());
}
// This function adds the edge
// between source to destination
public void addEdge(T source,
T destination,
boolean bidirectional)
{
if (!map.containsKey(source))
addVertex(source);
if (!map.containsKey(destination))
addVertex(destination);
map.get(source).add(destination);
if (bidirectional == true) {
map.get(destination).add(source);
}
}
// This function gives the count of vertices
public void getVertexCount()
{
System.out.println("The graph has "
+ map.keySet().size()
+ " vertex");
}
// This function gives the count of edges
public void getEdgesCount(boolean bidirection)
{
int count = 0;
for (T v : map.keySet()) {
count += map.get(v).size();
}
if (bidirection == true) {
count = count / 2;
}
System.out.println("The graph has "
+ count
+ " edges.");
}
// This function gives whether
// a vertex is present or not.
public void hasVertex(T s)
{
if (map.containsKey(s)) {
System.out.println("The graph contains "
+ s + " as a vertex.");
}
else {
System.out.println("The graph does not contain "
+ s + " as a vertex.");
}
}
// This function gives whether an edge is present or not.
public void hasEdge(T s, T d)
{
if (map.get(s).contains(d)) {
System.out.println("The graph has an edge between "
+ s + " and " + d + ".");
}
else {
System.out.println("The graph has no edge between "
+ s + " and " + d + ".");
}
}
// Prints the adjancency list of each vertex.
@Override
public String toString()
{
StringBuilder builder = new StringBuilder();
for (T v : map.keySet()) {
builder.append(v.toString() + ": ");
for (T w : map.get(v)) {
builder.append(w.toString() + " ");
}
builder.append("\n");
}
return (builder.toString());
}
}
// Driver Code
public class Main {
public static void main(String args[])
{
// Object of graph is created.
Graph<Integer> g = new Graph<Integer>();
// edges are added.
// Since the graph is bidirectional,
// so boolean bidirectional is passed as true.
g.addEdge(0, 1, true);
g.addEdge(0, 4, true);
g.addEdge(1, 2, true);
g.addEdge(1, 3, true);
g.addEdge(1, 4, true);
g.addEdge(2, 3, true);
g.addEdge(3, 4, true);
// Printing the graph
System.out.println("Graph:\n"
+ g.toString());
// Gives the no of vertices in the graph.
g.getVertexCount();
// Gives the no of edges in the graph.
g.getEdgesCount(true);
// Tells whether the edge is present or not.
g.hasEdge(3, 4);
// Tells whether vertex is present or not
g.hasVertex(5);
}
}
Output:
Graph:
0: 1 4
1: 0 2 3 4
2: 1 3
3: 1 2 4
4: 0 1 3
The graph has 5 vertex
The graph has 7 edges.
The graph has an edge between 3 and 4.
The graph does not contain 5 as a vertex.
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