solved 트리의 지름 - 828ms 118.468mb

Baekjoon/트리의지름/트리의지름_옥수빈.java

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+import java.awt.*;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+import java.util.List;
+
+public class Main {
+    static Map<Integer, List<Point>> costMap;
+    static boolean[] visited;
+    static int maxDistance = 0;
+    static int farthestNode = 0;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int V = Integer.parseInt(br.readLine());
+        costMap = new HashMap<>();
+
+        for (int i = 1; i <= V; i++) {
+            costMap.put(i, new ArrayList<>());
+        }
+
+        for (int v = 0; v < V; v++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int s = Integer.parseInt(st.nextToken());
+            while (true) {
+                int e = Integer.parseInt(st.nextToken());
+                if (e == -1) break;
+                int c = Integer.parseInt(st.nextToken());
+                costMap.get(s).add(new Point(e, c));
+            }
+        }
+
+        visited = new boolean[V + 1];
+        dfs(1, 0);
+
+        visited = new boolean[V + 1];
+        maxDistance = 0;
+        dfs(farthestNode, 0);
+
+        System.out.println(maxDistance);
+    }
+
+    public static void dfs(int now, int cost) {
+        if (cost > maxDistance) {
+            maxDistance = cost;
+            farthestNode = now;
+        }
+
+        visited[now] = true;
+        for (Point p : costMap.get(now)) {
+            if (!visited[p.x]) {
+                dfs(p.x, cost + p.y);
+            }
+        }
+    }
+}