1987 알파벳

#include <stdio.h>
 
int arr[30][30] = { 0 };
int r, c, rstLen = 0;
int visit[100] = { 0 };
 
void DFS(int y, int x, int len);
 
int main() {
    scanf("%d %d", &r, &c);
 
    for (int i = 0; i < r; i++) {
        char str[50];
        scanf("%s", str);
 
        for (int j = 0; j < 50; j++) {
            if (str[j] == '\0')
                break;
            else
                arr[i][j] = (int)(str[j] - 'A'+1);
        }
    }
 
    visit[arr[0][0]] = 1;
 
    DFS(0, 0, 1);
 
    printf("%d", rstLen);
}
 
void DFS(int y, int x, int len) {
    if (len > rstLen) {
        rstLen = len;
    }
 
    if (y - 1 >= 0) {
        int alpha = arr[y - 1][x];
        if (visit[alpha] == 0) {
            visit[alpha] = 1;
 
            DFS(y - 1, x, len + 1);
            visit[alpha] = 0;
        }
    }
    if (y + 1 < r) {
        int alpha = arr[y + 1][x];
        if (visit[alpha] == 0) {
            visit[alpha] = 1;
 
            DFS(y + 1, x, len + 1);
            visit[alpha] = 0;
        }
    }
    if (x - 1 >= 0) {
        int alpha = arr[y][x-1];
        if (visit[alpha] == 0) {
            visit[alpha] = 1;
 
            DFS(y, x - 1, len + 1);
            visit[alpha] = 0;
        }
    }
    if (x + 1 < c) {
        int alpha = arr[y][x+1];
        if (visit[alpha] == 0) {
            visit[alpha] = 1;
 
            DFS(y, x + 1, len + 1);
            visit[alpha] = 0;
        }
    }
}