231028 표 병합

private static final int MAX_SIZE = 2501;
private int[] parent = new int[MAX_SIZE];
private String[] value = new String[MAX_SIZE];

public String[] solution(String[] commands) {
	initialize();

	List<String> result = new ArrayList<>();
	for (String command : commands) {
		StringTokenizer st = new StringTokenizer(command);
		String cmd = st.nextToken();

		switch (cmd) {
			case "UPDATE":
				handleUpdateCommand(st);
				break;
			case "MERGE":
				handleMergeCommand(st);
				break;
			case "UNMERGE":
				handleUnmergeCommand(st);
				break;
			case "PRINT":
				handlePrintCommand(st, result);
				break;
			default:
				break;
		}
	}

	return result.toArray(new String[0]);
}

private void initialize() {
	for (int i = 1; i < MAX_SIZE; i++) {
		parent[i] = i;
		value[i] = "";
	}
}

private void handleUpdateCommand(StringTokenizer st) {
	if (st.countTokens() == 2) {
		String before = st.nextToken();
		String after = st.nextToken();
		for (int i = 1; i < MAX_SIZE; i++) {
			if (before.equals(value[i])) {
				value[i] = after;
			}
		}
	} else {
		int x = Integer.parseInt(st.nextToken());
		int y = Integer.parseInt(st.nextToken());
		String after = st.nextToken();
		int num = convertNum(x, y);
		value[find(num)] = after;
	}
}

private void handleMergeCommand(StringTokenizer st) {
	int x1 = Integer.parseInt(st.nextToken());
	int y1 = Integer.parseInt(st.nextToken());
	int x2 = Integer.parseInt(st.nextToken());
	int y2 = Integer.parseInt(st.nextToken());
	int n1 = convertNum(x1, y1);
	int n2 = convertNum(x2, y2);
	int root1 = find(n1);
	int root2 = find(n2);

	if (root1 == root2) {
		return;
	}

	String rootString = value[root1].isBlank() ? value[root2] : value[root1];
	value[root1] = "";
	value[root2] = "";
	union(root1, root2);
	value[root1] = rootString;
}

private void handleUnmergeCommand(StringTokenizer st) {
	int x = Integer.parseInt(st.nextToken());
	int y = Integer.parseInt(st.nextToken());
	int num = convertNum(x, y);
	int root = find(num);
	String rootString1 = value[root];
	value[root] = "";
	value[num] = rootString1;
	List<Integer> deleteList = new ArrayList<>();

	for (int i = 1; i < MAX_SIZE; i++) {
		if (find(i) == root) {
			deleteList.add(i);
		}
	}

	for (Integer t : deleteList) {
		parent[t] = t;
	}
}

private void handlePrintCommand(StringTokenizer st, List<String> result) {
	int printX = Integer.parseInt(st.nextToken());
	int printY = Integer.parseInt(st.nextToken());
	int printNum = convertNum(printX, printY);
	int printRoot = find(printNum);

	if (value[printRoot].isBlank()) {
		result.add("EMPTY");
	} else {
		result.add(value[printRoot]);
	}
}

private int find(int a) {
	if (parent[a] == a) {
		return a;
	} else {
		parent[a] = find(parent[a]);
		return parent[a];
	}
}

private void union(int a, int b) {
	a = find(a);
	b = find(b);
	if (a != b) {
		parent[b] = a;
	}
}

private int convertNum(int x, int y) {
	return 50 * (x - 1) + y;
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/150366