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]);
		}
	}
}