图论——邻接表HashSet,TreeSet存储
前言
上一小节已经说过邻接表了,用的是LinkedList数组存储,这一小节用另外两个数据结构。
HashSet性能最高,但是集合中元素无序
TreeSet性能略逊HashSet,基本无影响,集合中元素有序
HashSet
public class AdjHashSet {
private int V;//顶点数
private int E;//边数
private HashSet<Integer>[] adj;//邻接表,HashSet数组存储
public AdjHashSet(String filename){
File file = new File(filename);
try(Scanner scanner = new Scanner(file)){
V = scanner.nextInt();//顶点数
if(V<=0) throw new RuntimeException("顶点个数必须大于0");
adj = new HashSet[V];
for(int i=0;i<V;i++){
adj[i] = new HashSet<>();
}
E = scanner.nextInt();//边数
if(E<0) throw new RuntimeException("边数不能为负数");
for(int i=0;i<E;i++){
int a = scanner.nextInt();
validateVertex(a);
int b = scanner.nextInt();
validateVertex(b);
//自环边检测
if(a==b){
throw new RuntimeException("简单图不能包含自环边");
}
//平行边检测
if(adj[a].contains(b)){
throw new RuntimeException("简单图不能包含平行边");
}
adj[a].add(b);
adj[b].add(a);
}
}catch (IOException e){
e.printStackTrace();
}
}
private void validateVertex(int v){
if(v<0||v>=V){
throw new RuntimeException("顶点下标溢出");
}
}
public int vertexNum(){
return V;
}
public int edgeNum(){
return E;
}
public boolean hasEdge(int v,int w){
validateVertex(v);
validateVertex(w);
return adj[v].contains(w);
}
//邻接顶点
public Iterable<Integer> adj(int v){
validateVertex(v);
return adj[v];
}
//度
public int degree(int v){
validateVertex(v);
return adj[v].size();
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(String.format("V = %d,E = %d\n",V,E));
for(int i=0;i<adj.length;i++){
sb.append(i+":");
for (Iterator<Integer> it = adj[i].iterator(); it.hasNext(); ) {
sb.append(it.next()+" ");
}
sb.append("\n");
}
return sb.toString();
}
public static void main(String[] args) {
AdjHashSet adjList = new AdjHashSet("graph.txt");
System.out.println(adjList);
System.out.println(adjList.degree(4));
}
}
TreeSet
public class AdjTreeSet {
private int V;//顶点数
private int E;//边数
private TreeSet<Integer>[] adj;//邻接表,TreeSet数组存储
public AdjTreeSet(String filename){
File file = new File(filename);
try(Scanner scanner = new Scanner(file)){
V = scanner.nextInt();//顶点数
if(V<=0) throw new RuntimeException("顶点个数必须大于0");
adj = new TreeSet[V];
for(int i=0;i<V;i++){
adj[i] = new TreeSet<>();
}
E = scanner.nextInt();//边数
if(E<0) throw new RuntimeException("边数不能为负数");
for(int i=0;i<E;i++){
int a = scanner.nextInt();
validateVertex(a);
int b = scanner.nextInt();
validateVertex(b);
//自环边检测
if(a==b){
throw new RuntimeException("简单图不能包含自环边");
}
//平行边检测
if(adj[a].contains(b)){
throw new RuntimeException("简单图不能包含平行边");
}
adj[a].add(b);
adj[b].add(a);
}
}catch (IOException e){
e.printStackTrace();
}
}
private void validateVertex(int v){
if(v<0||v>=V){
throw new RuntimeException("顶点下标溢出");
}
}
public int vertexNum(){
return V;
}
public int edgeNum(){
return E;
}
public boolean hasEdge(int v,int w){
validateVertex(v);
validateVertex(w);
return adj[v].contains(w);
}
//邻接顶点
public Iterable<Integer> adj(int v){
validateVertex(v);
return adj[v];
}
//度
public int degree(int v){
validateVertex(v);
return adj[v].size();
}
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append(String.format("V = %d,E = %d\n",V,E));
for(int i=0;i<adj.length;i++){
sb.append(i+":");
for (Iterator<Integer> it = adj[i].iterator(); it.hasNext(); ) {
sb.append(it.next()+" ");
}
sb.append("\n");
}
return sb.toString();
}
public static void main(String[] args) {
AdjTreeSet adjList = new AdjTreeSet("graph.txt");
System.out.println(adjList);
System.out.println(adjList.degree(4));
}
}
graph.txt
7 6
0 1
0 2
1 3
2 6
2 3
1 4