Merge pull request #760 from AlgorithmWithGod/Ukj0ng

[20250828] BOJ / G4 / 두 단계 최단 경로 1 / 한종욱

Author: ShinHeeEul

Ukj0ng/202508/28 BOJ G4 두 단계 최단 경로 1.md

@@ -0,0 +1,95 @@
+```
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    private static final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    private static final BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    private static final long INF = (long)2e10 + 10;
+    private static List<Node>[] graph;
+    private static long[] dist;
+    private static int N, M, X, Y, Z;
+
+    public static void main(String[] args) throws IOException {
+        init();
+
+        dijkstra(X, 0);
+        long result = dist[Y];
+        dijkstra(Y, 0);
+        result += dist[Z];
+        if (result > INF) {
+            bw.write("-1 ");
+        } else {
+            bw.write(result + " ");
+        }
+
+        dijkstra(X, Y);
+        if (dist[Z] == INF) {
+            bw.write("-1 ");
+        } else {
+            bw.write(dist[Z] + " ");
+        }
+
+        bw.flush();
+        bw.close();
+        br.close();
+    }
+
+    private static void init() throws IOException {
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+
+        graph = new List[N+1];
+        dist =  new long[N+1];
+        for (int i = 1; i <= N; i++) {
+            graph[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(st.nextToken());
+            int b = Integer.parseInt(st.nextToken());
+            int cost = Integer.parseInt(st.nextToken());
+
+            graph[a].add(new Node(b, cost));
+        }
+
+        st = new StringTokenizer(br.readLine());
+        X = Integer.parseInt(st.nextToken());
+        Y = Integer.parseInt(st.nextToken());
+        Z = Integer.parseInt(st.nextToken());
+    }
+
+    private static void dijkstra(int start, int stopover) {
+        PriorityQueue<Node> pq = new PriorityQueue<>((o1, o2) -> Long.compare(o1.cost, o2.cost));
+        Arrays.fill(dist, INF);
+        dist[start] = 0;
+        pq.add(new Node(start, 0));
+
+        while (!pq.isEmpty()) {
+            Node current = pq.poll();
+
+            if (current.cost > dist[current.dest]) continue;
+
+            for (Node next : graph[current.dest]) {
+                if (next.dest == stopover) continue;
+                if (current.cost + next.cost < dist[next.dest]) {
+                    dist[next.dest] = current.cost + next.cost;
+                    pq.add(new Node(next.dest, dist[next.dest]));
+                }
+            }
+        }
+    }
+
+    static class Node {
+        int dest;
+        long cost;
+
+        Node(int dest, long cost) {
+            this.dest = dest;
+            this.cost = cost;
+        }
+    }
+}
+```