[20250227] BOJ / 골드3 / 파티 / 김수연

suyeun84/202502/27 BOJ G3 파티.md

@@ -0,0 +1,68 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class boj1238 {
+	static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+	static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	static StringTokenizer st;
+
+	static void nextLine() throws Exception {st = new StringTokenizer(br.readLine());}
+	static int nextInt() {return Integer.parseInt(st.nextToken());}
+	static void end() throws Exception {bw.flush();bw.close();br.close();}
+
+	static ArrayList<ArrayList<Node>> graph = new ArrayList<>();
+	static int N, M, X;
+
+	public static void main(String[] args) throws Exception {
+		nextLine();
+		N = nextInt();
+		M = nextInt();
+		X = nextInt();
+		int S, E, T, answer = 0;
+		for (int i = 0; i < N+1; i++) graph.add(new ArrayList<>());
+
+		for (int i = 0; i < M; i++) {
+			nextLine();
+			S = nextInt();
+			E = nextInt();
+			T = nextInt();
+			graph.get(S).add(new Node(T, E));
+		}
+
+		for (int i = 1; i < N+1; i++) {
+			answer = Math.max(answer, dijkstra(i, X) + dijkstra(X, i));
+		}
+		bw.write(answer+"\n");
+		end();
+	}
+
+	static int dijkstra(int start, int target) {
+		if (start == target) return 0;
+		PriorityQueue<Node> pq = new PriorityQueue<>((o1, o2) -> o1.t-o2.t);
+		int[] dist = new int[N+1];
+		Arrays.fill(dist, Integer.MAX_VALUE);
+		dist[start] = 0;
+		pq.add(new Node(0, start));
+		while (!pq.isEmpty()) {
+			Node curr = pq.poll(); //시간 가장 작은 것
+			if (dist[curr.e] < curr.t) continue;
+			dist[curr.e] = curr.t;
+			for (Node n : graph.get(curr.e)) {
+				if (n.t+dist[curr.e] >= dist[n.e]) continue;
+				pq.add(new Node(n.t+dist[curr.e], n.e));
+			}
+		}
+		return dist[target];
+	}
+
+	static class Node {
+		int t;
+		int e;
+		public Node(int t, int e) {
+			this.t = t;
+			this.e = e;
+		}
+	}
+}
+```