[JAVA-자바] 1504번: 특정한 최단 경로

 

 

소스코드:

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.PriorityQueue;
import java.util.StringTokenizer;

public class Main {
    public static class Node {
        int to;
        int cost;

        Node(int t, int c) {
            this.to = t;
            this.cost = c;
        }
    }

    static BufferedReader br;
    static BufferedWriter bw;

    static List<List<Node>> nodeList;
    static int N, E, U, V;

    public static void main(String[] args) throws IOException {
        br = new BufferedReader(new InputStreamReader(System.in));
        bw = new BufferedWriter(new OutputStreamWriter(System.out));

        StringTokenizer st = new StringTokenizer(br.readLine());
        N = Integer.parseInt(st.nextToken());
        E = Integer.parseInt(st.nextToken());

        nodeList = new ArrayList<>();
        for (int i = 0; i <= N; i++) {
            nodeList.add(new ArrayList<>());
        }
        for (int i = 0; i < E; i++) {
            st = new StringTokenizer(br.readLine());
            int start = Integer.parseInt(st.nextToken());
            int to = Integer.parseInt(st.nextToken());
            int cost = Integer.parseInt(st.nextToken());
            nodeList.get(start).add(new Node(to, cost));
            nodeList.get(to).add(new Node(start, cost));
        }
        st = new StringTokenizer(br.readLine());
        U = Integer.parseInt(st.nextToken());
        V = Integer.parseInt(st.nextToken());
        br.close();

        int[] from1 = dijkstra(1, N);
        int[] fromU = dijkstra(U, N);
        int[] fromV = dijkstra(V, N);

        int U_V_N;
        if (from1[U] == Integer.MAX_VALUE || fromU[V] == Integer.MAX_VALUE || fromV[N] == Integer.MAX_VALUE) {
            U_V_N = -1;
        } else {
            U_V_N = from1[U] + fromU[V] + fromV[N];
        }

        int V_U_N;
        if (from1[V] == Integer.MAX_VALUE || fromV[U] == Integer.MAX_VALUE || fromU[N] == Integer.MAX_VALUE) {
            V_U_N = -1;
        } else {
            V_U_N = from1[V] + fromV[U] + fromU[N];
        }

        int result;
        if (U_V_N == -1 && V_U_N == -1) {
            result = -1;
        } else if (U_V_N == -1) {
            result = V_U_N;
        } else if (V_U_N == -1) {
            result = U_V_N;
        } else {
            result = Math.min(U_V_N, V_U_N);
        }

        bw.write(result + "\n");
        bw.close();
    }

    public static int[] dijkstra(int start, int to) {
        int[] distance = new int[N + 1];
        Arrays.fill(distance, Integer.MAX_VALUE);

        distance[start] = 0;
        PriorityQueue<Node> pq = new PriorityQueue<>((o1, o2) -> o1.cost - o2.cost);
        pq.add(new Node(start, 0));

        while (!pq.isEmpty()) {
            Node current = pq.poll();

            if (current.cost > distance[current.to]) {
                continue;
            }

            for (Node next : nodeList.get(current.to)) {
                if (distance[next.to] > current.cost + next.cost) {
                    distance[next.to] = current.cost + next.cost;
                    pq.add(new Node(next.to, distance[next.to]));
                }
            }
        }
        return distance;
    }

}

 

글의 내용 중 잘못된 점이나 수정이 필요한 부분, 혹은 궁금한 사항이 있다면 언제든 댓글로 남겨주시면 감사하겠습니다.

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