BOJ1167_트리의지름구하기 java solution

mong3125/DFS/BOJ1167_트리의지름구하기.java

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+package DFS;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.ArrayList;
+import java.util.StringTokenizer;
+
+public class BOJ1167_트리의지름구하기 {
+
+    static ArrayList<Edge>[] edges;
+    static boolean[] visited;
+    static int max;
+    static int farthest;
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        int V = Integer.parseInt(br.readLine());
+        edges = new ArrayList[V + 1];
+        for (int i = 0; i < V + 1; i++) {
+            edges[i] = new ArrayList<>();
+        }
+
+        for (int i = 0; i < V; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int a = Integer.parseInt(st.nextToken());
+
+            while (true) {
+                int node = Integer.parseInt(st.nextToken());
+                if (node == -1) break;
+
+                int cost = Integer.parseInt(st.nextToken());
+                edges[a].add(new Edge(node, cost));
+            }
+        }
+
+        max = 0;
+        visited = new boolean[V+1];
+        dfs(1, 0);
+
+        max = 0;
+        visited = new boolean[V+1];
+        dfs(farthest, 0);
+
+        System.out.println(max);
+    }
+
+    public static void dfs(int node, int cost) {
+        visited[node] = true;
+        if (cost > max) {
+            farthest = node;
+            max = cost;
+        }
+
+        for (Edge edge : edges[node]) {
+            if (!visited[edge.node]) {
+                dfs(edge.node, cost + edge.cost);
+            }
+        }
+    }
+
+    static class Edge {
+        int node;
+        int cost;
+
+        public Edge(int node, int cost) {
+            this.node = node;
+            this.cost = cost;
+        }
+    }
+}