Another update from ingydotnet^djgoku

Task/Permutations/Python/permutations-2.py

@@ -0,0 +1,26 @@
+def perm1(n):
+    a = list(range(n))
+    def sub(i):
+        if i == n - 1:
+            yield tuple(a)
+        else:
+            for k in range(i, n):
+                a[i], a[k] = a[k], a[i]
+                yield from sub(i + 1)
+                a[i], a[k] = a[k], a[i]
+    yield from sub(0)
+
+def perm2(n):
+    a = list(range(n))
+    def sub(i):
+        if i == n - 1:
+            yield tuple(a)
+        else:
+            for k in range(i, n):
+                a[i], a[k] = a[k], a[i]
+                yield from sub(i + 1)
+            x = a[i]
+            for k in range(i + 1, n):
+                a[k - 1] = a[k]
+            a[n - 1] = x
+    yield from sub(0)

Task/Permutations/Python/permutations-3.py

@@ -0,0 +1,15 @@
+for u in perm1(3): print(u)
+(0, 1, 2)
+(0, 2, 1)
+(1, 0, 2)
+(1, 2, 0)
+(2, 1, 0)
+(2, 0, 1)
+
+for u in perm2(3): print(u)
+(0, 1, 2)
+(0, 2, 1)
+(1, 0, 2)
+(1, 2, 0)
+(2, 0, 1)
+(2, 1, 0)

Task/Permutations/Python/permutations-4.py

@@ -0,0 +1,39 @@
+def nextperm(a):
+    n = len(a)
+    i = n - 1
+    while i > 0 and a[i - 1] > a[i]:
+        i -= 1
+    j = i
+    k = n - 1
+    while j < k:
+        a[j], a[k] = a[k], a[j]
+        j += 1
+        k -= 1
+    if i == 0:
+        return False
+    else:
+        j = i
+        while a[j] < a[i - 1]:
+            j += 1
+        a[i - 1], a[j] = a[j], a[i - 1]
+        return True
+
+def perm3(n):
+    if type(n) is int:
+        if n < 1:
+            return []
+        a = list(range(n))
+    else:
+        a = sorted(n)
+    u = [tuple(a)]
+    while nextperm(a):
+        u.append(tuple(a))
+    return u
+
+for p in perm3(3): print(p)
+(0, 1, 2)
+(0, 2, 1)
+(1, 0, 2)
+(1, 2, 0)
+(2, 0, 1)
+(2, 1, 0)