Prim 算法

求无向图的最小生成树：

import java.util.ArrayList;import java.util.Arrays;import java.util.List;public class Prim {List<int[]> allPath=new ArrayList<int[]>();public int prim(int[][] graph,int start){int[] dis=new int[graph.length];int[] path=new int[graph.length];Arrays.fill(path,start);int re=0;for(int i=0;i<graph.length;i++){dis[i]=graph[start][i];}boolean[] flag=new boolean[graph.length];flag[start]=true;for(int k=0;k<graph.length-1;k++){int pos=-1;int min=Integer.MAX_VALUE;for(int i=0;i<dis.length;i++){if(!flag[i]&&min>dis[i]){min=dis[i];pos=i;}}if(pos==-1) return -1;int[] temp={path[pos],pos,graph[path[pos]][pos]};allPath.add(temp);flag[pos]=true;re+=dis[pos];for(int j=0;j<dis.length;j++){if(!flag[j]&&dis[j]>graph[pos][j]){dis[j]=graph[pos][j];path[j]=pos;}}}return re;}public static void main(String[] args) {int m=6;int[][] input={  {1,2,6},  {1,3,1},  {1,4,5},  {2,3,5},  {2,5,3},  {3,4,5},  {3,5,6},{3,6,4},  {4,6,2},  {5,6,6}  };Prim s=new Prim();int[][] graph=new int[m][m];for(int i=0;i<m;i++){for(int j=0;j<m;j++){graph[i][j]=Integer.MAX_VALUE;}}for(int i=0;i<input.length;i++){graph[input[i][0]-1][input[i][1]-1]=input[i][2];graph[input[i][1]-1][input[i][0]-1]=input[i][2];}System.out.println(s.prim(graph, 4));for(int i=0;i<s.allPath.size();i++){int[] temp=s.allPath.get(i);System.out.println(temp[0]+" ---> "+temp[1]+":"+temp[2]);}}}