From 58cde38c315491e03188726954eb5d2d25046a42 Mon Sep 17 00:00:00 2001
From: JHLEE325 <82587652+JHLEE325@users.noreply.github.com>
Date: Fri, 19 Dec 2025 18:02:28 +0900
Subject: [PATCH] =?UTF-8?q?[20251219]=20BOJ=20/=20G4=20/=20Tree=20/=20?=
 =?UTF-8?q?=EC=9D=B4=EC=A4=80=ED=9D=AC?=
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---
 JHLEE325/202512/19 BOJ G4 Tree.md | 76 +++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 JHLEE325/202512/19 BOJ G4 Tree.md

diff --git a/JHLEE325/202512/19 BOJ G4 Tree.md b/JHLEE325/202512/19 BOJ G4 Tree.md
new file mode 100644
index 00000000..9b2694ca
--- /dev/null
+++ b/JHLEE325/202512/19 BOJ G4 Tree.md	
@@ -0,0 +1,76 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static List<Integer>[] graph;
+    static boolean[] visited;
+    static boolean isgraph;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringBuilder sb = new StringBuilder();
+
+        int T = Integer.parseInt(br.readLine());
+
+        for (int t=0;t<T;t++) {
+            StringTokenizer st;
+            int N = Integer.parseInt(br.readLine());
+            int M = Integer.parseInt(br.readLine());
+
+            graph = new ArrayList[N + 1];
+            visited = new boolean[N + 1];
+            isgraph = false;
+
+            for (int i = 1; i <= N; i++) {
+                graph[i] = new ArrayList<>();
+            }
+
+            for (int i = 0; i < M; i++) {
+                st = new StringTokenizer(br.readLine());
+                int a = Integer.parseInt(st.nextToken());
+                int b = Integer.parseInt(st.nextToken());
+
+                graph[a].add(b);
+                graph[b].add(a);
+            }
+
+            if (M != N - 1) {
+                sb.append("graph\n");
+                continue;
+            }
+
+            dfs(1, -1);
+
+            boolean connected = true;
+            for (int i = 1; i <= N; i++) {
+                if (!visited[i]) {
+                    connected = false;
+                    break;
+                }
+            }
+
+            if (isgraph || !connected) {
+                sb.append("graph\n");
+            } else {
+                sb.append("tree\n");
+            }
+        }
+
+        System.out.print(sb);
+    }
+
+    static void dfs(int cur, int parent) {
+        visited[cur] = true;
+
+        for (int next : graph[cur]) {
+            if (!visited[next]) {
+                dfs(next, cur);
+            } else if (next != parent) {
+                isgraph = true;
+            }
+        }
+    }
+}
+```