Merge pull request #900 from AlgorithmWithGod/khj20006

[20250915] BOJ / G3 / 그래프 리뷰 유튜버 / 권혁준

Author: ShinHeeEul

khj20006/202509/15 BOJ G3 그래프 리뷰 유튜버.md

@@ -0,0 +1,109 @@
+```java
+import java.io.*;
+import java.util.*;
+
+class IOController {
+    BufferedReader br;
+    BufferedWriter bw;
+    StringTokenizer st;
+
+    public IOController() {
+        br = new BufferedReader(new InputStreamReader(System.in));
+        bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        st = new StringTokenizer("");
+    }
+
+    String nextLine() throws Exception {
+        String line = br.readLine();
+        st = new StringTokenizer(line);
+        return line;
+    }
+
+    String nextToken() throws Exception {
+        while (!st.hasMoreTokens())
+            nextLine();
+        return st.nextToken();
+    }
+
+    int nextInt() throws Exception {
+        return Integer.parseInt(nextToken());
+    }
+
+    long nextLong() throws Exception {
+        return Long.parseLong(nextToken());
+    }
+
+    double nextDouble() throws Exception {
+        return Double.parseDouble(nextToken());
+    }
+
+    void close() throws Exception {
+        bw.flush();
+        bw.close();
+    }
+
+    void write(String content) throws Exception {
+        bw.write(content);
+    }
+
+}
+
+public class Main {
+
+    static IOController io;
+
+    //
+
+    static int N;
+    static int[] c;
+    static List<Integer>[] graph;
+
+    public static void main(String[] args) throws Exception {
+
+        io = new IOController();
+
+        N = io.nextInt();
+        c = new int[N+1];
+        graph = new List[N+1];
+        for(int i=1;i<=N;i++) graph[i] = new ArrayList<>();
+
+        for(int i=1;i<N;i++) {
+            int a = io.nextInt();
+            int b = io.nextInt();
+            c[a]++;
+            c[b]++;
+            graph[a].add(b);
+            graph[b].add(a);
+        }
+
+        for(int i=1;i<=N;i++) if(c[i] >= 3) {
+            int a = graph[i].get(0);
+            int b = graph[i].get(1);
+            int c = graph[i].get(2);
+            io.write("3\n");
+            io.write(a + " " + b + "\n");
+            io.write(b + " " + c + "\n");
+            io.write(a + " " + c + "\n");
+            io.close();
+            return;
+        }
+
+        for(int i=1;i<=N;i++) for(int j:graph[i]) {
+            if(c[i] == 2 && c[j] == 2) {
+                int a = graph[i].get(0);
+                if(a == j) a = graph[i].get(1);
+                int b = graph[j].get(0);
+                if(b == i) b = graph[j].get(1);
+                io.write("3\n");
+                io.write(a + " " + b + "\n");
+                io.write(a + " " + j + "\n");
+                io.write(b + " " + i + "\n");
+                io.close();
+                return;
+            }
+        }
+
+    }
+
+}
+```