240912 집합의 표현

private static int n;
private static int[] parents;

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	StringBuilder sb = new StringBuilder();
	StringTokenizer st = new StringTokenizer(br.readLine());

	n = Integer.parseInt(st.nextToken());
	int m = Integer.parseInt(st.nextToken());

	parents = new int[n + 1];
	initializeParents();

	for (int i = 0; i < m; i++) {
		st = new StringTokenizer(br.readLine());
		int command = Integer.parseInt(st.nextToken());
		int x = Integer.parseInt(st.nextToken());
		int y = Integer.parseInt(st.nextToken());

		if (command == 0) {
			union(x, y);
		} else {
			sb.append(isSameParent(x, y) ? "YES\n" : "NO\n");
		}
	}

	System.out.print(sb);
}

private static void initializeParents() {
	for (int i = 1; i <= n; i++) {
		parents[i] = i;
	}
}

private static int find(int x) {
	if (x == parents[x]) {
		return x;
	}
	parents[x] = find(parents[x]);
	return parents[x];
}

private static void union(int x, int y) {
	int rootX = find(x);
	int rootY = find(y);

	if (rootX != rootY) {
		if (rootX > rootY) {
			parents[rootY] = rootX;
		} else {
			parents[rootX] = rootY;
		}
	}
}

private static boolean isSameParent(int x, int y) {
	return find(x) == find(y);
}

출처:https://www.acmicpc.net/problem/1717