[20250613] BOJ / G3 / 파티 / 설진영

Seol-JY/202506/13 BOJ G3 파티.md

@@ -0,0 +1,90 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+    static int N, M, X;
+    static ArrayList<ArrayList<Node>> graph;
+    static ArrayList<ArrayList<Node>> reverseGraph;
+    static int[] distToX;
+    static int[] distFromX;
+
+    static class Node {
+        int vertex;
+        int cost;
+
+        Node(int vertex, int cost) {
+            this.vertex = vertex;
+            this.cost = cost;
+        }
+    }
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        X = Integer.parseInt(st.nextToken());
+
+        graph = new ArrayList<>();
+        reverseGraph = new ArrayList<>();
+
+        for (int i = 0; i <= N; i++) {
+            graph.add(new ArrayList<>());
+            reverseGraph.add(new ArrayList<>());
+        }
+
+        for (int i = 0; i < M; i++) {
+            st = new StringTokenizer(br.readLine());
+            int start = Integer.parseInt(st.nextToken());
+            int end = Integer.parseInt(st.nextToken());
+            int time = Integer.parseInt(st.nextToken());
+
+            graph.get(start).add(new Node(end, time));
+            reverseGraph.get(end).add(new Node(start, time));
+        }
+
+        distToX = new int[N + 1];
+        distFromX = new int[N + 1];
+
+        dijkstra(X, graph, distFromX);
+        dijkstra(X, reverseGraph, distToX);
+
+        int maxTime = 0;
+        for (int i = 1; i <= N; i++) {
+            if (i != X) {
+                maxTime = Math.max(maxTime, distToX[i] + distFromX[i]);
+            }
+        }
+
+        System.out.println(maxTime);
+    }
+
+    static void dijkstra(int start, ArrayList<ArrayList<Node>> targetGraph, int[] dist) {
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        PriorityQueue<Node> pq = new PriorityQueue<>((a, b) -> Integer.compare(a.cost, b.cost));
+
+        dist[start] = 0;
+        pq.offer(new Node(start, 0));
+
+        while (!pq.isEmpty()) {
+            Node current = pq.poll();
+            int currentVertex = current.vertex;
+            int currentCost = current.cost;
+
+            if (currentCost > dist[currentVertex]) continue;
+
+            for (Node next : targetGraph.get(currentVertex)) {
+                int nextVertex = next.vertex;
+                int nextCost = currentCost + next.cost;
+
+                if (nextCost < dist[nextVertex]) {
+                    dist[nextVertex] = nextCost;
+                    pq.offer(new Node(nextVertex, nextCost));
+                }
+            }
+        }
+    }
+}
+```