[10주차] 이혜원 #138

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	import java.io.*;
	import java.util.*;

	public class HW_회전하는_빙하 {
	static class Node {
	int x, y;
	public Node(int x, int y) {
	this.x = x;
	this.y = y;
	}
	}

	static int n, q, L;
	static int[][] board, nextboard;
	static boolean[][] visited;
	static int[] dx = {0, 1, -1, 0}; // 오른쪽, 아래, 위, 왼쪽
	static int[] dy = {1, 0, 0, -1};
	static int max = 0;

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

	n = Integer.parseInt(st.nextToken()); // 격자의 크기 (2^n * 2^n)
	q = Integer.parseInt(st.nextToken()); // 회전 횟수
	L = (int) Math.pow(2, n);
	board = new int[L][L];
	nextboard = new int[L][L];

	// 보드 입력
	for (int i = 0; i < L; i++) {
	st = new StringTokenizer(br.readLine());
	for (int j = 0; j < L; j++) {
	board[i][j] = Integer.parseInt(st.nextToken());
	}
	}

	// 회전 레벨 입력
	st = new StringTokenizer(br.readLine());
	while (q-- > 0) {
	int lv = Integer.parseInt(st.nextToken());
	if (lv > 0) rotate(lv);
	melt();
	}

	// 1. 남아있는 빙하의 총량 계산
	int sum = 0;
	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	sum += board[i][j];
	}
	}
	System.out.println(sum);

	// 2. 가장 큰 얼음 군집 크기 계산
	visited = new boolean[L][L];
	max = 0;
	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	if (!visited[i][j] && board[i][j] > 0) {
	max = Math.max(max, bfs(i, j));
	}
	}
	}
	System.out.println(max);
	}

	// 초기화
	public static void initialize() {
	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	nextboard[i][j] = 0;
	}
	}
	}


	public static void rotate(int level) {
	initialize(); // `nextboard` 초기화
	int boxSize = (int) Math.pow(2, level);
	int halfSize = (int) Math.pow(2, level - 1);

	for (int i = 0; i < L; i += boxSize) { // 시계 방향 90도 회전
	for (int j = 0; j < L; j += boxSize) {
	move(i, j, halfSize, 0);
	move(i, j + halfSize, halfSize, 1);
	move(i + halfSize, j, halfSize, 2);
	move(i + halfSize, j + halfSize, halfSize, 3);
	}
	}

	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	board[i][j] = nextboard[i][j]; // 배열 복사
	}
	}
	}

	// size`만큼의 하위 격자를 시계 방향으로 회전
	public static void move(int startX, int startY, int size, int dir) {
	for (int i = startX; i < startX + size; i++) {
	for (int j = startY; j < startY + size; j++) {
	int nx = i + dx[dir] * size;
	int ny = j + dy[dir] * size;
	if (!isValid(nx, ny)) continue;
	nextboard[nx][ny] = board[i][j];
	}
	}
	}

	public static void melt() {
	initialize();

	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	if (board[i][j] != 0 && iceCnt(i, j) < 3) {
	nextboard[i][j] = board[i][j] - 1; // -1
	} else {
	nextboard[i][j] = board[i][j];
	}
	}
	}

	for (int i = 0; i < L; i++) {
	for (int j = 0; j < L; j++) {
	board[i][j] = nextboard[i][j];
	}
	}
Comment on lines +124 to +128 Copy link Contributor @KodaHye KodaHye Nov 13, 2024 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. `nextboard`를 전역변수로 선언하지 않고, `melt()` 함수 안에 있는 지역변수로 선언한 뒤, 이 과정을 `board = nextboard`로 해도 될 것 같습니다! Copy link Contributor Author @icegosimperson icegosimperson Nov 15, 2024 Choose a reason for hiding this comment The reason will be displayed to describe this comment to others. Learn more. nextboard를 지역 변수로 선언하면 불필요한 반복 줄일 수 있겠네요! 피드백 감사합니다👍
	}

	public static int iceCnt(int x, int y) {
	int cnt = 0;
	for (int d = 0; d < 4; d++) {
	int nx = x + dx[d];
	int ny = y + dy[d];

	if (isValid(nx, ny) && board[nx][ny] != 0) {
	cnt++;
	}
	}
	return cnt;
	}

	// BFS : 얼음 군집 크기를 계산
	public static int bfs(int x, int y) {
	int size = 1;
	Queue<int[]> queue = new LinkedList<>();
	queue.offer(new int[]{x, y});
	visited[x][y] = true;

	while (!queue.isEmpty()) {
	int[] pos = queue.poll();

	for (int d = 0; d < 4; d++) {
	int nx = pos[0] + dx[d];
	int ny = pos[1] + dy[d];

	if (isValid(nx, ny) && !visited[nx][ny] && board[nx][ny] > 0) {
	visited[nx][ny] = true;
	queue.offer(new int[]{nx, ny});
	size++;
	}
	}
	}
	return size;
	}

	public static boolean isValid(int x, int y) {
	return x >= 0 && y >= 0 && x < L && y < L;
	}
	}

5 changes: 5 additions & 0 deletions SQL/10주차/HW_Second Highest Salary.SQL

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	SELECT MAX(Salary) as SecondHighestSalary
	FROM (SELECT salary, dense_rank() over(order by salary desc) as rk
	FROM Employee
	) Employee
	where rk = 2;

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[10주차] 이혜원 #138

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@KodaHye KodaHye Nov 13, 2024

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@icegosimperson icegosimperson Nov 15, 2024

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