文章目录
- 带权图
- 1.1带权图的实现
- 1.2 完整代码
带权图
1.1带权图的实现
在无向无权图的基础上,增加边的权。
使用TreeMap存储边的权重。
- 遍历输入文件,创建TreeMap adj存储每个节点。
- 每个输入的adj节点链接新的TreeMap,存储相邻的边和权重
private TreeMap<Integer, Integer>[] adj;adj = new TreeMap[V];for(int i = 0; i < V; i ++)adj[i] = new TreeMap<Integer, Integer>();
- 两条边相连,则分别把权重加入各自的邻接表中
adj[a].put(b, weight);
adj[b].put(a, weight);
- 判断两点之间是否有边
public boolean hasEdge(int v, int w){validateVertex(v);validateVertex(w);return adj[v].containsKey(w);
}
- 求相邻的所有节点
public Iterable<Integer> adj(int v){validateVertex(v);return adj[v].keySet();
}
- 求两点的权值
public int getWeight(int v, int w){if(hasEdge(v, w)) return adj[v].get(w);throw new IllegalArgumentException(String.format("No edge %d-%d", v, w));
}
- 移除边
public void removeEdge(int v, int w){validateVertex(v);validateVertex(w);if(adj[v].containsKey(w)) E --;adj[v].remove(w);adj[w].remove(v);
}
- 复制一个图
public Object clone(){try{WeightedGraph cloned = (WeightedGraph) super.clone();cloned.adj = new TreeMap[V];for(int v = 0; v < V; v ++){cloned.adj[v] = new TreeMap<Integer, Integer>();for(Map.Entry<Integer, Integer> entry: adj[v].entrySet())cloned.adj[v].put(entry.getKey(), entry.getValue());}return cloned;}catch (CloneNotSupportedException e){e.printStackTrace();}return null;
}
1.2 完整代码
package Chapter09_Weight_Graph;import java.io.File;
import java.io.IOException;
import java.util.Map;
import java.util.TreeMap;
import java.util.Scanner;/// 暂时只支持无向带权图
public class WeightedGraph implements Cloneable{private int V;private int E;private TreeMap<Integer, Integer>[] adj;public WeightedGraph(String filename){File file = new File(filename);try(Scanner scanner = new Scanner(file)){V = scanner.nextInt();if(V < 0) throw new IllegalArgumentException("V must be non-negative");adj = new TreeMap[V];for(int i = 0; i < V; i ++)adj[i] = new TreeMap<Integer, Integer>();E = scanner.nextInt();if(E < 0) throw new IllegalArgumentException("E must be non-negative");for(int i = 0; i < E; i ++){int a = scanner.nextInt();validateVertex(a);int b = scanner.nextInt();validateVertex(b);int weight = scanner.nextInt();if(a == b) throw new IllegalArgumentException("Self Loop is Detected!");if(adj[a].containsKey(b)) throw new IllegalArgumentException("Parallel Edges are Detected!");adj[a].put(b, weight);adj[b].put(a, weight);}}catch(IOException e){e.printStackTrace();}}public void validateVertex(int v){if(v < 0 || v >= V)throw new IllegalArgumentException("vertex " + v + "is invalid");}public int V(){return V;}public int E(){return E;}public boolean hasEdge(int v, int w){validateVertex(v);validateVertex(w);return adj[v].containsKey(w);}public Iterable<Integer> adj(int v){validateVertex(v);return adj[v].keySet();}public int getWeight(int v, int w){if(hasEdge(v, w)) return adj[v].get(w);throw new IllegalArgumentException(String.format("No edge %d-%d", v, w));}public int degree(int v){validateVertex(v);return adj[v].size();}public void removeEdge(int v, int w){validateVertex(v);validateVertex(w);if(adj[v].containsKey(w)) E --;adj[v].remove(w);adj[w].remove(v);}@Overridepublic Object clone(){try{WeightedGraph cloned = (WeightedGraph) super.clone();cloned.adj = new TreeMap[V];for(int v = 0; v < V; v ++){cloned.adj[v] = new TreeMap<Integer, Integer>();for(Map.Entry<Integer, Integer> entry: adj[v].entrySet())cloned.adj[v].put(entry.getKey(), entry.getValue());}return cloned;}catch (CloneNotSupportedException e){e.printStackTrace();}return null;}@Overridepublic String toString(){StringBuilder sb = new StringBuilder();sb.append(String.format("V = %d, E = %d\n", V, E));for(int v = 0; v < V; v ++){sb.append(String.format("%d : ", v));for(Map.Entry<Integer, Integer> entry: adj[v].entrySet())sb.append(String.format("(%d: %d) ", entry.getKey(), entry.getValue()));sb.append('\n');}return sb.toString();}public static void main(String[] args){WeightedGraph g = new WeightedGraph("gw1.txt");System.out.print(g);}
}