prim 最小生成树算法 java实现

import java.io.BufferedInputStream;
import java.util.Scanner;



public class Prim {

    static int[][] arr;
    static boolean flag[];  //用来标记节点i是否被覆盖
    static int n;
    static int sum;
    static final int maxInt = Integer.MAX_VALUE;
    public static void main(String[] args) {
        Scanner s = new Scanner(new BufferedInputStream(System.in));
        while(s.hasNextInt()){
            n = s.nextInt();
            arr = new int[n+1][n+1];
            flag = new boolean[n+1];
            for(int i=1; i<=n; i++)
                for(int j=1; j<=n; j++)
                    arr[i][j] = s.nextInt(); //从下标1开始存储
            
            sum = 0;
            flag[1] = true; //选取第一个节点
            
            for(int k=1; k<n; k++){    //循环n-1次
                int min = maxInt,min_i = 0;
                for(int i=1; i<=n; i++){
                    if( !flag[i] && arr[1][i] < min){
                        min = arr[1][i];
                        min_i = i;
                    }
                }
                System.out.println("  min_i:"+min_i);
                flag[min_i] = true; // 覆盖节点
                

                for(int i=1; i<=n; i++){  //更新未覆盖节点的距离,每加入一个点就更新
                    if( !flag[i] && arr[1][i] > arr[min_i][i])
                        arr[1][i] = arr[min_i][i];
                    System.out.print("arr[1]["+i+"]"+arr[1][i]+" ");
                }
                System.out.println();
                sum += arr[1][min_i];//加上权值
            }
            
            
            System.out.println(sum);
            
        }
    }

}