расстановки ферзей

queens.py

@@ -0,0 +1,45 @@
+# import itertools
+
+# def is_valid(positions):
+#     for i in range(len(positions)):
+#         for j in range(i + 1, len(positions)):
+#             if abs(positions[i] - positions[j]) == j - i:
+#                 return False
+#     return True
+
+# def count_n_queens_bf(N):
+#     count = 0
+#     for perm in itertools.permutations(range(N)):
+#         if is_valid(perm):
+#             count += 1
+#     return count
+#N = 4  # пример для N=8
+#print(count_n_queens_bf(N))
+
+
+
+
+def is_safe(queens, row, col):
+    for r, c in enumerate(queens):
+        if c == col or abs(r - row) == abs(c - col):
+            return False
+    return True
+
+def backtrack(row, queens, N):
+    if row == N:
+        return 1
+    count = 0
+    for col in range(N):
+        if is_safe(queens, row, col):
+            count += backtrack(row + 1, queens + [col], N)
+    return count
+
+def count_n_queens_bt(N):
+    return backtrack(0, [], N)
+
+N = 4
+print(count_n_queens_bt(N))
+
+
+N = 4
+print(count_n_queens_bit(N))