250306-棋盘问题 bfs解法

openjudge/323/2400011491.md

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+# 状态: [Accepted](http://dsbpython.openjudge.cn/dspythonbook/solution/49114558/)
+
+```
+基本信息
+#:49326210
+题目:250603
+提交人:2400011491王思杰(24n2400011491)
+内存:9276kB
+时间:134ms
+语言:Python3
+提交时间:2025-06-02 15:45:21
+```
+# 思路
+用bfs递归，在剪枝后能达到

openjudge/323/2400011491.py

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+from collections import deque
+
+def bfs(plat,n,k):
+    q=deque([(0,0,0)])
+    ans = 0
+    while q:#确定当前位置
+        for _ in range(len(q)):
+            l,m,placed=q.popleft()
+            if placed==k:
+                ans+=1
+                continue
+            if n - m < k - placed:
+                continue
+            for i in range(n):
+                if not l & 1<<i and plat[m][i]=="#":
+                    q.append((l | (1<<i),m+1,placed+1))
+            q.append((l,m+1,placed))
+    return ans
+
+while True:
+    n,k = map(int,input().split())
+    if n==k==-1:
+        break
+    plat = [input() for _ in range(n)]
+    print(bfs(plat,n,k))