[20251026] BOJ / G4 / Tree / 김민진

zinnnn37/202510/26 BOJ G4 Tree.md

@@ -0,0 +1,78 @@
+```java
+import java.io.*;
+import java.util.StringTokenizer;
+
+public class BJ_13244_Tree {
+
+	private static final BufferedReader  br = new BufferedReader(new InputStreamReader(System.in));
+	private static final BufferedWriter  bw = new BufferedWriter(new OutputStreamWriter(System.out));
+	private static final StringBuilder   sb = new StringBuilder();
+	private static       StringTokenizer st;
+
+	private static int T, N, M;
+	private static int[] parents;
+
+	public static void main(String[] args) throws IOException {
+		T = Integer.parseInt(br.readLine());
+
+		while (T-- > 0) {
+			init();
+			sol();
+		}
+		bw.write(sb.toString());
+		bw.flush();
+		bw.close();
+		br.close();
+	}
+
+	private static void init() throws IOException {
+		N = Integer.parseInt(br.readLine());
+		M = Integer.parseInt(br.readLine());
+
+		parents = new int[N + 1];
+		for (int i = 1; i < N + 1; i++) {
+			parents[i] = i;
+		}
+	}
+
+	private static void sol() throws IOException {
+		boolean isTree = true;
+		for (int i = 0; i < M; i++) {
+			st = new StringTokenizer(br.readLine());
+
+			int a = Integer.parseInt(st.nextToken());
+			int b = Integer.parseInt(st.nextToken());
+
+			if (!union(a, b)) {
+				isTree = false;
+			}
+		}
+
+		if (M != N - 1) {
+			isTree = false;
+		}
+		sb.append(isTree ? "tree\n" : "graph\n");
+	}
+
+	private static int find(int a) {
+		if (parents[a] == a) return a;
+
+		return parents[a] = find(parents[a]);
+	}
+
+	private static boolean union(int a, int b) {
+		int rootA = find(a);
+		int rootB = find(b);
+
+		if (rootA == rootB) return false;
+
+		if (rootA < rootB) {
+			parents[rootB] = rootA;
+		} else {
+			parents[rootA] = rootB;
+		}
+		return true;
+	}
+
+}
+```