September Morn Update

Task/N-queens-problem/Python/n-queens-problem-5.py

@@ -1,23 +1,11 @@
-def queens(n):
-    a = list(range(n))
-    up = [True]*(2*n - 1)
-    down = [True]*(2*n - 1)
-    def sub(i):
-        if i == n:
-            yield tuple(a)
-        else:
-            for k in range(i, n):
-                j = a[k]
-                p = i + j
-                q = i - j + n - 1
-                if up[p] and down[q]:
-                    up[p] = down[q] = False
-                    a[i], a[k] = a[k], a[i]
-                    yield from sub(i + 1)
-                    up[p] = down[q] = True
-                    a[i], a[k] = a[k], a[i]
-    yield from sub(0)
+def solve(n, i, a, b, c):
+    if i < n:
+        for j in range(n):
+            if j not in a and i+j not in b and i-j not in c:
+                for solution in solve(n, i+1, a+[j], b+[i+j], c+[i-j]):
+                    yield solution
+    else:
+        yield a
 
-#Count solutions for n=8:
-sum(1 for p in queens(8))
-92
+for solution in solve(8, 0, [], [], []):
+    print(solution)