leetcode-go/written-exam/tencent-2018-spring/Painter.java

import java.util.Scanner;

public class Painter {
    private static int N = 0, M = 0;

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        N = scanner.nextInt();
        M = scanner.nextInt();
        scanner.nextLine(); // !!important
        char[][] board = new char[N][M];
        for (int i = 0; i < N; i++) {
            board[i] = scanner.nextLine().toCharArray();
        }
        int cnt = 0;
        for (int i = 0; i < N; i++) {
            for (int j = 0; j < M; j++) {
                switch (board[i][j]) {
                    case 'G':
                        cnt++;
                        dfs(board, j, i, 1, 1, 'Y', 'B');
                    case 'B':
                        cnt++;
                        dfs(board, j, i, 1, -1, 'B', 'Y');
                        break;
                    case 'Y':
                        cnt++;
                        dfs(board, j, i, 1, 1, 'Y', 'B');
                        break;
                    default:
                        break;
                }
            }
        }
        System.out.println(cnt);
        scanner.close();
    }

    private static void dfs(char[][] board, int x, int y, int dx, int dy, char curr, char next) {
        if (x < 0 || M <= x || y < 0 || N <= y || board[y][x] == 'X' || board[y][x] == next) return;
        if (board[y][x] == curr) {
            board[y][x] = 'X';
        } else if (board[y][x] == 'G') {
            board[y][x] = next;
        }
        dfs(board, x+dx, y+dy, dx, dy, curr, next);
        dfs(board, x-dx, y-dy, dx, dy, curr, next);
    }
}