Merge pull request #438 from AlgorithmWithGod/03do-new30

[20250711] BOJ / G3 / 파티 / 신동윤

Author: ShinHeeEul

03do-new30/202507/11 BOJ G3 파티.md

@@ -0,0 +1,67 @@
+```java
+import java.io.*;
+import java.util.*;
+
+
+public class Main {
+    static int N, M, X;
+    static int[][] arr, revArr;
+
+    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());
+
+        arr = new int[N+1][N+1]; // 정방향 (a->b)
+        revArr = new int[N+1][N+1]; // 역방향 (a<-b)
+        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 c = Integer.parseInt(st.nextToken());
+            arr[a][b] = c;
+            revArr[b][a] = c;
+        }
+
+        int[] fromX = dijkstra(X);
+        
+        arr = revArr;
+        int[] toX = dijkstra(X);
+
+        int answer = 0;
+        for (int i = 1; i <= N; i++) {
+            answer = Math.max(answer, fromX[i] + toX[i]);
+        }
+        System.out.println(answer);
+        br.close();
+    }
+
+    private static int[] dijkstra(int start) {
+        int[] dist = new int[N+1];
+        Arrays.fill(dist, Integer.MAX_VALUE);
+        dist[start] = 0;
+        PriorityQueue<int[]> pq = new PriorityQueue<>(new Comparator<int[]>() {
+            @Override
+            public int compare(int[] o1, int[] o2) {
+                return Integer.compare(o1[0], o2[0]);
+            }
+        });
+        pq.offer(new int[] {0, start}); // (cost, node)
+        while (!pq.isEmpty()) {
+            int[] info = pq.poll();
+            int node = info[1];
+            for (int nextNode = 1; nextNode <= N; nextNode++) {
+                if (arr[node][nextNode] == 0) continue;
+                int newDist = dist[node] + arr[node][nextNode];
+                if (dist[nextNode] > newDist) {
+                    dist[nextNode] = newDist;
+                    pq.offer(new int[] {newDist, nextNode});
+                }
+            }
+        }
+        return dist;
+    }
+}
+```