[20250905] BOJ / G3 / 파티 / 김민진

zinnnn37/202509/6 BOJ G3 파티.md

@@ -0,0 +1,113 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class BJ_1238_파티 {
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final 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[]        aDist;
+	private static int[]        dDist;
+	private static List<Node>[] asc;
+	private static List<Node>[] desc;
+
+	static class Node implements Comparable<Node> {
+		int end;
+		int weight;
+
+		public Node(int end, int weight) {
+			this.end    = end;
+			this.weight = weight;
+		}
+
+		@Override
+		public int compareTo(Node o) {
+			return Integer.compare(this.weight, o.weight);
+		}
+	}
+
+	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());
+		X = Integer.parseInt(st.nextToken());
+
+		asc  = new List[N + 1];
+		desc = new List[N + 1];
+		for (int i = 1; i <= N; i++) {
+			asc[i]  = new ArrayList<>();
+			desc[i] = new ArrayList<>();
+		}
+		for (int i = 0; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+
+			int u = Integer.parseInt(st.nextToken());
+			int v = Integer.parseInt(st.nextToken());
+			int w = Integer.parseInt(st.nextToken());
+
+			asc[u].add(new Node(v, w));
+			desc[v].add(new Node(u, w));
+		}
+	}
+
+	private static void sol() throws IOException {
+		aDist = dijkstra(X, desc);
+		dDist = dijkstra(X, asc);
+
+		int maxTime = 0;
+		for (int i = 1; i <= N; i++) {
+			if (i != X) {
+				maxTime = Math.max(maxTime, aDist[i] + dDist[i]);
+			}
+		}
+
+		bw.write(maxTime + "");
+		bw.flush();
+		bw.close();
+		br.close();
+	}
+
+	private static int[] dijkstra(int start, List<Node>[] graph) {
+		PriorityQueue<Node> pq = new PriorityQueue<>();
+
+		int[] dist = new int[N + 1];
+		Arrays.fill(dist, Integer.MAX_VALUE);
+
+		dist[start] = 0;
+		pq.offer(new Node(start, 0));
+
+		while (!pq.isEmpty()) {
+			Node current   = pq.poll();
+			int  curEnd    = current.end;
+			int  curWeight = current.weight;
+
+			if (curWeight > dist[curEnd]) continue;
+
+			for (Node next : graph[curEnd]) {
+				int nextEnd    = next.end;
+				int nextWeight = next.weight;
+
+				int newDist = dist[curEnd] + nextWeight;
+
+				if (newDist < dist[nextEnd]) {
+					dist[nextEnd] = newDist;
+					pq.offer(new Node(nextEnd, newDist));
+				}
+			}
+		}
+		return dist;
+	}
+}
+```