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.metadata/.plugins/org.eclipse.core.resources/.history/1/20c4cfb80ba8001715918e2c1fc31ded
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| package minimal_spanning_tree; | ||
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| import java.io.InputStream; | ||
| import java.util.ArrayList; | ||
| import java.util.Arrays; | ||
| import java.util.HashMap; | ||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Scanner; | ||
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| /** | ||
| * 最小生成树的prim算法，从一个节点出发，每次找到与所有加入的节点相邻的节点，权重最小的节点加入，不能形成环。 | ||
| * | ||
| * @author liyafei | ||
| * | ||
| */ | ||
| public class MSTPrim { | ||
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| List list=new ArrayList<>(); | ||
| int count=1; | ||
| double[][] weights; | ||
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| class Node{ | ||
| Node link; | ||
| Node pre; | ||
| int weight; | ||
| int key; | ||
| int start; | ||
| int end; | ||
| } | ||
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| /** | ||
| * prim 算法求最小生成树,给定根节点，开始找相邻节点的最小值，算法每一步在连接集合A和A之外的节点的所有边中 | ||
| * 选择一条轻量级边加入到A中 | ||
| * 用一个列表将遍历过的轻量级边的节点存储起来，然后看新的轻量级边的两点是否在列表中，如果在，就不加入。 | ||
| * @param r 根节点 | ||
| * 注意：图的矩阵表示形式是对称的，可以利用 | ||
| */ | ||
| public void mstprim(int r){ | ||
| List list2=new ArrayList<>(); | ||
| for (int i = 0; i < weights.length; i++) { | ||
| Node node=(Node) list.get(i); | ||
| node.key=Integer.MAX_VALUE; | ||
| node.pre=null; | ||
| } | ||
| // Node node=(Node) list.get(r); | ||
| // node.key=0; | ||
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| // double[] arr=weights[r-1]; //取出给定顶点相邻节点的权重值，然后找出几行几列。排序 | ||
| // double min = Double.MAX_VALUE; | ||
| // int index=0; //角标值 | ||
| // for (int i = 0; i < arr.length; i++) { | ||
| // if(arr[i]>0 && arr[i]<min){ | ||
| // min=arr[i]; | ||
| // index=i; | ||
| // } | ||
| // } | ||
| //(r,index)这条线被包括进来了 | ||
| // list2.add(r); | ||
| // if(!list2.contains(index)){ | ||
| // list2.add(index); | ||
| // } | ||
| Map map=new HashMap(); | ||
| list2.add(r); | ||
| while(list2.size()<2){ | ||
| double minest=Double.MAX_VALUE; | ||
| int index2=0; | ||
| for (int i = 0; i < list2.size(); i++) { | ||
| double[] arr2=weights[(int) list2.get(i)]; | ||
| int key=(int) list2.get(i); | ||
| for (int j = 0; j < arr2.length; j++) { | ||
| if(arr2[j]>0 && arr2[j]<minest){ | ||
| System.out.println(arr2[j]); | ||
| if(!list2.contains(j)){ | ||
| minest=arr2[j]; | ||
| index2=j; | ||
| map.put(key, index2); | ||
| // System.out.println(index2); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| list2.add(index2); | ||
| } | ||
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| // double[] weis=weights[index]; | ||
| // double[][] afteriter=new double[2][weights.length]; | ||
| // afteriter[0]=arr; | ||
| // afteriter[1]=weis; | ||
| for (int i = 0; i < list2.size(); i++) { | ||
| System.out.println("key "+list2.get(i)); | ||
| // System.out.println("value "+map.get(list2.get(i))); | ||
| } | ||
| // System.out.println(list2.size()); | ||
| // System.out.println(min); | ||
| // System.out.println(index); | ||
| // | ||
| } | ||
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| /** | ||
| * 得到创建的带有权重的图，读出相邻节点之间的距离，然后存储到二维数组weights中。 | ||
| * 权重图的大小比节点多1，但是角标为0的位置都没用，为了处理存储的位置与节点的编号相一致 | ||
| */ | ||
| public double[][] getWeightArray(){ | ||
| weights=new double[list.size()][list.size()]; | ||
| for (int i = 0; i < list.size(); i++) { | ||
| Node node=(Node) list.get(i); | ||
| while(node!=null){ | ||
| int row=node.start-1; | ||
| int col=node.end-1; | ||
| double weight=node.weight; | ||
| weights[row][col]=weight; | ||
| node=node.link; | ||
| } | ||
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| } | ||
| return weights; | ||
| } | ||
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| /** | ||
| * 打印权重图 | ||
| */ | ||
| public void printWeightGraph(){ | ||
| double[][] weightsArray=getWeightArray(); | ||
| for (int i = 0; i < weightsArray.length; i++) { | ||
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| double[] wa=weightsArray[i]; | ||
| for (int j = 0; j < wa.length; j++) { | ||
| System.out.print(wa[j]+" "); | ||
| } | ||
| System.out.println(); | ||
| } | ||
| System.out.println(); | ||
| } | ||
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| /** | ||
| * 先构建带有权重的无向图。 | ||
| */ | ||
| public List createGraph(){ | ||
| Class clazz=this.getClass(); | ||
| InputStream ins=clazz.getResourceAsStream("/data.txt"); | ||
| Scanner scanner=new Scanner(ins); | ||
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| while(scanner.hasNextLine()){ | ||
| String s1=scanner.nextLine(); | ||
| Scanner oneLine=new Scanner(s1); | ||
| Node newNode; | ||
| Node first=null; | ||
| Node last=null; | ||
| while(oneLine.hasNext()){ | ||
| String s2=oneLine.next(); | ||
| int end=Integer.parseInt(s2); | ||
| if(end==999){ | ||
| break; | ||
| } | ||
| newNode=new Node(); | ||
| if(first!=null && oneLine.hasNext()){ | ||
| String s3=oneLine.next(); | ||
| int weight=Integer.parseInt(s3); | ||
| newNode.weight=weight; | ||
| } | ||
| newNode.start=count; | ||
| newNode.end=end; | ||
| newNode.link=null; | ||
| if(first==null){ | ||
| first=newNode; | ||
| last=newNode; | ||
| }else{ | ||
| last.link=newNode; | ||
| last=newNode; | ||
| } | ||
| } | ||
| list.add(first); | ||
| count++; | ||
| } | ||
| return list; | ||
| } | ||
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| } |
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