[20250824] BOJ / G4 / 두 단계 최단 경로 1 / 김민진

Author: zinnnn37

zinnnn37/202508/24 BOJ 23793 두 단계 최단 경로 1.md

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+```java
+import java.io.*;
+import java.util.*;
+
+public class BJ_23793_두_단계_최단_경로_1 {
+
+	private static BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static StringTokenizer st;
+
+	private static int N;
+	private static int M;
+	private static int X;
+	private static int Y;
+	private static int Z;
+
+	private static int[]        dist;
+	private static Queue<Node>  pq;
+	private static List<Node>[] graph;
+
+	private static class Node implements Comparable<Node> {
+		int to;
+		int weigh;
+
+		Node(int to, int weigh) {
+			this.to    = to;
+			this.weigh = weigh;
+		}
+
+		@Override
+		public int compareTo(Node o) {
+			return Integer.compare(this.weigh, o.weigh);
+		}
+	}
+
+	public static void main(String[] args) throws IOException {
+		init();
+		sol();
+	}
+
+	private static void init() throws IOException {
+		st = new StringTokenizer(br.readLine());
+		N  = Integer.parseInt(st.nextToken());
+		M  = Integer.parseInt(st.nextToken());
+
+		graph = new List[N + 1];
+		dist  = new int[N + 1];
+		for (int i = 1; i <= N; i++) {
+			graph[i] = new ArrayList<>();
+		}
+
+		pq = new PriorityQueue<>();
+		for (int i = 0; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+
+			int from   = Integer.parseInt(st.nextToken());
+			int to     = Integer.parseInt(st.nextToken());
+			int weight = Integer.parseInt(st.nextToken());
+
+			graph[from].add(new Node(to, weight));
+		}
+
+		st = new StringTokenizer(br.readLine());
+		X  = Integer.parseInt(st.nextToken());
+		Y  = Integer.parseInt(st.nextToken());
+		Z  = Integer.parseInt(st.nextToken());
+	}
+
+	private static void sol() throws IOException {
+		// 경유
+		int a = dijkstra(X, Y, false);
+		int b = dijkstra(Y, Z, false);
+		if (a == -1 || b == -1) {
+			bw.write("-1 ");
+		} else {
+			bw.write((a + b) + " ");
+		}
+
+		// 경유 X
+		bw.write(dijkstra(X, Z, true) + "");
+		bw.flush();
+		bw.close();
+		br.close();
+	}
+
+	private static int dijkstra(int from, int to, boolean flag) {
+		clear();
+		pq.offer(new Node(from, 0));
+		dist[from] = 0;
+
+		while (!pq.isEmpty()) {
+			Node cur = pq.poll();
+
+			if (cur.to == to) {
+				return cur.weigh;
+			}
+
+			if (dist[cur.to] < cur.weigh) {
+				continue;
+			}
+
+			for (Node n : graph[cur.to]) {
+				// Y를 경유하지 않아야하는데 경유함
+				if (flag && n.to == Y) {
+					continue;
+				}
+
+				int nextWeight = n.weigh + dist[cur.to];
+				if (nextWeight < dist[n.to]) {
+					dist[n.to] = nextWeight;
+					pq.offer(new Node(n.to, nextWeight));
+				}
+			}
+		}
+		return dist[to] != Integer.MAX_VALUE ? dist[to] : -1;
+	}
+
+	private static void clear() {
+		pq.clear();
+		Arrays.fill(dist, Integer.MAX_VALUE);
+	}
+
+}
+```