[백준, BOJ 10423] 전기가 부족해 (java)

https://www.acmicpc.net/problem/10423

10423번: 전기가 부족해

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메모리: 47,436 KB , 시간: 560  ms

사용 알고리즘: 그래프 이론, 최소 스패닝 트리

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

public class Main {

    static int[] parent;

    public static void main(String[] args) throws Exception{

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st;

        st = new StringTokenizer(br.readLine());
        int N = Integer.parseInt(st.nextToken());
        int M = Integer.parseInt(st.nextToken());
        int K = Integer.parseInt(st.nextToken());

        // 크루스칼 알고리즘 사용
        parent = new int[N + 1];
        for (int i = 1; i <= N; i++) {
            parent[i] = i;
        }

        st = new StringTokenizer(br.readLine());
        for (int i = 0; i < K; i++) {
            parent[Integer.parseInt(st.nextToken())] = 0;
        }

        PriorityQueue<int[]> pq = new PriorityQueue<>((o1, o2) -> o1[2] - o2[2]);
        int u, v, w;
        for (int i = 0; i < M; i++) {
            st = new StringTokenizer(br.readLine());
            u = Integer.parseInt(st.nextToken());
            v = Integer.parseInt(st.nextToken());
            w = Integer.parseInt(st.nextToken());

            pq.add(new int[] {u, v, w});
        }


        long result = 0;

        int[] now;
        while(!pq.isEmpty()) {
            now = pq.poll();

            if(union(now[0], now[1])) result += now[2];
        }

        System.out.println(result);
    }

    private static int find(int a) {
        if(parent[a] == a) return a;

        return parent[a] = find(parent[a]);
    }

    private static boolean union(int a, int b) {

        a = find(a);
        b = find(b);

        if(a == b) return false;

        if(a < b) parent[b] = a;
        else parent[a] = b;
        return true;
    }
}