예비군갈나이

<p>자바이긴 합니다...</p><pre><code class="language-java">package _4thweek;

import java.util.Scanner;

public class Baekjoon13244 {
    static int[] arr;

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int t = sc.nextInt();

        for (int tc = 0; tc < t; tc++) {
            int n = sc.nextInt();
            int m = sc.nextInt();
            boolean isTree = true;

            arr = new int[n + 1];

            if (m != n - 1) {
                isTree = false;
            }

            for (int i = 1; i <= n; i++) {
                arr[i] = i;
            }

            for (int i = 0; i < m; i++) {
                int parent = sc.nextInt();
                int child = sc.nextInt();

                if (!union(parent, child)) {
                    isTree = false;
                }
            }

            int root = find(1);
            for (int i = 1; i <= n; i++) {
                if (root != find(i)) {
                    isTree = false;
                    break;
                }
            }

            if (isTree) {
                System.out.println("tree");
            } else {
                System.out.println("graph");
            }
        }
    }

    static boolean union(int parent, int child) {
        int rootA = find(parent);
        int rootB = find(child);

        if (rootA == rootB) {
            return false;
        }
        arr[rootB] = rootA;
        return true;
    }

    static int find(int node) {
        if (arr[node] == node) {
            return node;
        }
        return arr[node] = find(arr[node]);
    }
}
</code></pre>

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