java 代码

import java.io.*;
import java.lang.*;
import java.util.*;

class Main{

    static int n = 0, m = 0, N = 100010;
    static PriorityQueue<int[]> q = new PriorityQueue<>((a, b)->{return a[2] - b[2];});//存储递增边长
    static int[] p = new int[N];
    static int find(int x){
        if(p[x] != x)p[x] = find(p[x]);
        return p[x];
    }

    public static void main(String[] args)throws Exception{
        BufferedReader buf = new BufferedReader(new InputStreamReader(System.in));
        String[] params = buf.readLine().split(" ");
        n = Integer.valueOf(params[0]);
        m = Integer.valueOf(params[1]);
        for(int i = 1; i <= m; ++i){
            String[] info = buf.readLine().split(" ");
            int a = Integer.valueOf(info[0]);
            int b = Integer.valueOf(info[1]);
            int w = Integer.valueOf(info[2]);
            int[] c = {a, b, w};
            q.offer(c);
        }
        for(int i = 1; i <= n; ++i){
            p[i] = i;
        }

        int res = 0;
        int cnt = 1;
        while(q.size() != 0){
            int[] c = q.poll();
            int a = find(c[0]);
            int b = find(c[1]);
            if(a != b){
                res += c[2];
                p[a] = b;
                cnt++;
            }
        }
        if(cnt == n){
            System.out.print(res);
        }else{
            System.out.print("impossible");
        }

    }
}