230801 2차원 동전 뒤집기

private int n, m;
private int[][] board;
private int[][] t;
private int answer;

public int solution(int[][] beginning, int[][] target) {
	answer = Integer.MAX_VALUE;
	n = beginning.length;
	m = beginning[0].length;

	board = beginning;
	t = target;

	dfs(0, 0);

	return (answer == Integer.MAX_VALUE) ? -1 : answer;
}

public void flipRow(int r) {
	for (int i = 0; i < m; i++) {
		board[r][i] = (board[r][i] + 1) % 2;
	}
}

public int compareCol(int c) {
	int check = 0;
	for (int i = 0; i < n; i++) {
		if (t[i][c] == board[i][c]) {
			check++;
		}
	}

	if (check == n) {
		return 0;
	} else if (check == 0) {
		return 1;
	}

	return -1;
}

public void dfs(int r, int cnt) {
	if (r == n) {
		boolean flag = true;
		for (int i = 0; i < m; i++) {
			int result = compareCol(i);
			if (result == -1) {
				flag = false;
				break;
			}
			cnt += result;
		}

		if (flag) {
			answer = Math.min(answer, cnt);
		}
		return;
	}

	flipRow(r);
	dfs(r + 1, cnt + 1);
	flipRow(r);

	dfs(r + 1, cnt);
}

출처:https://school.programmers.co.kr/learn/courses/30/lessons/131703