为3道题解补充Python版本（52.N皇后II / 207.课程表 / 1791.星型图中心）

problems/0052.N皇后II.md

@@ -305,3 +305,47 @@ class Solution {
 }
 ```
 
+### Python
+
+```python
+class Solution:
+    def totalNQueens(self, n: int) -> int:
+        count = 0
+        chessboard = [['.'] * n for _ in range(n)]  # 初始化棋盘
+
+        def is_valid(row: int, col: int) -> bool:
+            # 检查列是否有皇后
+            for i in range(row):
+                if chessboard[i][col] == 'Q':
+                    return False
+            # 检查45度角（左上）是否有皇后
+            i, j = row - 1, col - 1
+            while i >= 0 and j >= 0:
+                if chessboard[i][j] == 'Q':
+                    return False
+                i -= 1
+                j -= 1
+            # 检查135度角（右上）是否有皇后
+            i, j = row - 1, col + 1
+            while i >= 0 and j < n:
+                if chessboard[i][j] == 'Q':
+                    return False
+                i -= 1
+                j += 1
+            return True
+
+        def backtracking(row: int) -> None:
+            nonlocal count
+            if row == n:
+                count += 1
+                return
+            for col in range(n):
+                if is_valid(row, col):
+                    chessboard[row][col] = 'Q'  # 放置皇后
+                    backtracking(row + 1)
+                    chessboard[row][col] = '.'  # 回溯
+
+        backtracking(0)
+        return count
+```
+

problems/0207.课程表.md

@@ -57,3 +57,32 @@ public:
     }
 };
 ```
+
+## 其他语言版本
+
+### Python
+
+```python
+from collections import deque
+from typing import List
+
+class Solution:
+    def canFinish(self, numCourses: int, prerequisites: List[List[int]]) -> bool:
+        in_degree = [0] * numCourses              # 每门课程的入度
+        graph = [[] for _ in range(numCourses)]   # 邻接表：pre -> [后续课程]
+        for cur, pre in prerequisites:
+            # 上 cur 之前必须先上 pre，即 pre -> cur
+            graph[pre].append(cur)
+            in_degree[cur] += 1
+
+        que = deque([i for i in range(numCourses) if in_degree[i] == 0])  # 入度为0的课程入队
+        count = 0
+        while que:
+            cur = que.popleft()
+            count += 1                            # 已修课程数 +1
+            for nxt in graph[cur]:
+                in_degree[nxt] -= 1               # 后续课程入度 -1
+                if in_degree[nxt] == 0:
+                    que.append(nxt)
+        return count == numCourses
+```

problems/1791.找出星型图的中心节点.md

@@ -74,4 +74,23 @@ public:
 };
 ```
 
+## 其他语言版本
+
+### Python
+
+```python
+class Solution:
+    def findCenter(self, edges: List[List[int]]) -> int:
+        # 统计各个节点的度，只有中心节点的度会大于1
+        degree = {}
+        for u, v in edges:
+            degree[u] = degree.get(u, 0) + 1
+            degree[v] = degree.get(v, 0) + 1
+            if degree[u] > 1:
+                return u
+            if degree[v] > 1:
+                return v
+        return -1
+```
+