241224 2048 (Easy)

private static int n;
private static int max = 0;

public static void main(String[] args) throws IOException {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
	n = Integer.parseInt(br.readLine());

	int[][] map = new int[n][n];
	for (int i = 0; i < n; i++) {
		StringTokenizer st = new StringTokenizer(br.readLine(), " ");
		for (int j = 0; j < n; j++) {
			map[i][j] = Integer.parseInt(st.nextToken());
		}
	}

	backtracking(0, map);
	System.out.println(max);
}

private static void backtracking(int depth, int[][] map) {
	if (depth == 5) {
		updateMax(map);
		return;
	}

	for (int direction = 0; direction < 4; direction++) {
		int[][] newMap = deepCopy(map);
		swipe(newMap, direction);
		backtracking(depth + 1, newMap);
	}
}

private static void swipe(int[][] map, int direction) {
	switch (direction) {
		case 0:
			moveUp(map);
			break;
		case 1:
			moveDown(map);
			break;
		case 2:
			moveLeft(map);
			break;
		case 3:
			moveRight(map);
			break;
		default:
			break;
	}
}

private static void moveUp(int[][] map) {
	for (int col = 0; col < n; col++) {
		int index = 0, block = 0;
		for (int row = 0; row < n; row++) {
			if (map[row][col] != 0) {
				if (block == map[row][col]) {
					map[index - 1][col] *= 2;
					block = 0;
				} else {
					block = map[row][col];
					map[index++][col] = block;
				}
				if (index - 1 != row) {
					map[row][col] = 0;
				}
			}
		}
	}
}

private static void moveDown(int[][] map) {
	for (int col = 0; col < n; col++) {
		int index = n - 1, block = 0;
		for (int row = n - 1; row >= 0; row--) {
			if (map[row][col] != 0) {
				if (block == map[row][col]) {
					map[index + 1][col] *= 2;
					block = 0;
				} else {
					block = map[row][col];
					map[index--][col] = block;
				}
				if (index + 1 != row) {
					map[row][col] = 0;
				}
			}
		}
	}
}

private static void moveLeft(int[][] map) {
	for (int row = 0; row < n; row++) {
		int index = 0, block = 0;
		for (int col = 0; col < n; col++) {
			if (map[row][col] != 0) {
				if (block == map[row][col]) {
					map[row][index - 1] *= 2;
					block = 0;
				} else {
					block = map[row][col];
					map[row][index++] = block;
				}
				if (index - 1 != col) {
					map[row][col] = 0;
				}
			}
		}
	}
}

private static void moveRight(int[][] map) {
	for (int row = 0; row < n; row++) {
		int index = n - 1, block = 0;
		for (int col = n - 1; col >= 0; col--) {
			if (map[row][col] != 0) {
				if (block == map[row][col]) {
					map[row][index + 1] *= 2;
					block = 0;
				} else {
					block = map[row][col];
					map[row][index--] = block;
				}
				if (index + 1 != col) {
					map[row][col] = 0;
				}
			}
		}
	}
}

private static void updateMax(int[][] map) {
	for (int[] row : map) {
		for (int value : row) {
			if (max < value)
				max = value;
		}
	}
}

private static int[][] deepCopy(int[][] map) {
	int[][] newMap = new int[n][n];
	for (int i = 0; i < n; i++) {
		System.arraycopy(map[i], 0, newMap[i], 0, n);
	}
	return newMap;
}

출처:https://www.acmicpc.net/problem/12100