'commit'

TangDou/Dfs/DFS12_LQBS.cpp

@@ -0,0 +1,81 @@
+#include<bits/stdc++.h>
+
+using namespace std;
+const int N = 110;
+#define x first
+#define y second
+typedef pair<int, int> PII;
+int a[N][N];
+int dx[] = {-1, 1, 0, 0};
+int dy[] = {0, 0, -1, 1};
+
+int n, m, Max;
+vector<PII> 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;
+}