[JAVA] 백준 1987번- 알파벳

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

1987번: 알파벳

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

public class Main{
    static int[][] arr;
    static boolean[] alpha;
    static int[] dx = {-1, 0, 1, 0};
    static int[] dy = {0, 1, 0, -1};
    static int r, c;
    static int answer = 0;
    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());

        arr = new int[r][c];
        alpha = new boolean[26];

        for(int i=0; i<r; i++){
            String str = br.readLine();
            for(int j=0; j<c; j++){
                arr[i][j] = str.charAt(j)-65;
            }
        }

        alpha[arr[0][0]] = true;
        dfs(0, 0, 1);

        System.out.println(answer);
    }
    static void dfs(int x, int y, int cnt) {

        answer = Math.max(answer, cnt);

        for (int i = 0; i < 4; i++) {
            int nx = x + dx[i];
            int ny = y + dy[i];

            if (nx < 0 || nx >= r || ny < 0 || ny >= c || alpha[arr[nx][ny]]) continue;

            alpha[arr[nx][ny]] = true; // 나온 알파벳으로 체크
            dfs(nx, ny, cnt + 1);
            alpha[arr[nx][ny]] = false; // 복구
        }
    }
}