2589 보물섬

#include <stdio.h>
#include <string.h>
#include <queue>
 
using namespace std;
 
char arr[55][55] = {0};
char chk[55][55] = { 0 };
int dx[4] = { 1,-1,0,0 };
int dy[4] = { 0,0,1,-1 };
int row, col;
 
typedef struct _dot {
    int len;
    int y;
    int x;
}dot;
 
int bfs(int y, int x) {
    queue<dot> q;
    memcpy(chk, arr, sizeof(arr));
    q.push({ 0,y,x });
    chk[y][x] = -1;
 
    int len;
    while (!q.empty()) {
        len = q.front().len;
        int y = q.front().y;
        int x = q.front().x;
 
        q.pop();
 
        int rst = 0;
        for (int i = 0; i < 4; i++) {
            int xx = x + dx[i];
            int yy = y + dy[i];
 
            if (xx <= 0 || xx > col || yy <= 0 || yy > row) 
                continue;            
            if (chk[yy][xx] != 'L') 
                continue;
            
            chk[yy][xx] = -1;
            q.push({ len + 1, yy, xx });        
        }
    }
    return len;
}
 
int main() {
    scanf("%d %d", &row, &col);
 
    for (int i = 1; i <= row; i++) {
        char tmp[55];
        scanf("%s", &tmp);
 
        for (int j = 1; j <= col; j++) {
            arr[i][j] = tmp[j - 1];
        }
    }
 
    int maxN = -1;
    for (int i = 1; i <= row; i++) {
        for (int j = 1; j <= col; j++) {
            if (arr[i][j] == 'L') {
                int tmp = bfs(i, j);
                if (tmp > maxN)
                    maxN = tmp;
            }
        }
    }
 
    printf("%d", maxN);
}