[백준] 1987. 알파벳

https://www.acmicpc.net/problem/1987

1987번: 알파벳

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import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {
	
	
	static int R, C, answer, cnt;
	static char[][] map;
	static boolean[][] visited;
	static int[][] dir = {{0,1},{1,0},{0,-1},{-1,0}};
	static boolean[] check;
	
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		StringTokenizer st = new StringTokenizer(br.readLine(), " ");
		
		R = Integer.parseInt(st.nextToken());
		C = Integer.parseInt(st.nextToken());
		
		map = new char[R][C];
		
		for(int i=0; i<R; i++) {
			String s = br.readLine();
			for(int j=0; j<C; j++) {
				map[i][j] = s.charAt(j);
			}
		}
		
		visited = new boolean[R][C];
		check = new boolean[91];
		
		DFS(0, 0);
		
		System.out.println(answer+1);
	}
	
	public static void DFS(int x, int y) {
		
		answer = Math.max(cnt, answer);
		visited[x][y] = true;
		check[map[x][y]] = true;
		
		for(int i=0; i<4; i++) {
			int nx = x + dir[i][0];
			int ny = y + dir[i][1];
			
			if(isInside(nx, ny) && !visited[nx][ny] && !check[map[nx][ny]]) {
				cnt++;
				visited[nx][ny] = true;
				check[map[nx][ny]] = true;
				DFS(nx, ny);
				visited[nx][ny] = false;
				check[map[nx][ny]] = false;
				cnt--;
			}
		}
	}
	
	public static boolean isInside(int x, int y) {
		return x>=0 && x<R && y>=0 && y<C;
	}
}