#include using namespace std; const int N = 110; #define x first #define y second typedef pair PII; int a[N][N]; int dx[] = {-1, 1, 0, 0}; int dy[] = {0, 0, -1, 1}; int n, m, Max; vector s; /** 测试数据 4 4 BLQB BBQS SBQL QQQQ 输出 2 3 3 LSB QBQ BSL 输出 -1 */ /** * 功能:深度优先搜索 * @param x 横坐标 * @param y 纵坐标 * @param step 步数 */ void dfs(int x, int y, int step) { //如果死循环,一直 if (step > n * m) { cout << -1 << endl; exit(0); } //更新步数 Max = max(Max, step); //4个方向 for (int i = 0; i <= 3; i++) { int tx = x + dx[i]; int ty = y + dy[i]; //如果出界 if (tx < 1 || tx > n || ty < 1 || ty > m) continue; //下一步与期望值对比 if (a[tx][ty] == a[x][y] + 1 || (a[tx][ty] == 1 && a[x][y] == 4)) dfs(tx, ty, step + 1); } } int main() { cin >> n >> m; for (int i = 1; i <= n; i++) for (int j = 1; j <= m; j++) { char x; cin >> x; //记录起点 if (x == 'L') a[i][j] = 1, s.push_back({i, j}); else if (x == 'Q') a[i][j] = 2; else if (x == 'B') a[i][j] = 3; else if (x == 'S') a[i][j] = 4; } //模拟从每个起点开始 for (int i = 0; i < s.size(); i++) dfs(s[i].x, s[i].y, 1); //长度除以4 cout << Max / 4 << endl; return 0; }