Data commit

Task/Permutations-by-swapping/BASIC256/permutations-by-swapping.basic

@@ -0,0 +1,38 @@
+call perms(3)
+print
+call perms(4)
+end
+
+subroutine perms(n)
+    dim p((n+1)*4)
+    for i = 1 to n
+        p[i] = -i
+    next i
+    s = 1
+
+    do
+        print "Perm: [ ";
+        for i = 1 to n
+            print abs(p[i]); " ";
+        next i
+        print "] Sign: "; s
+
+        k = 0
+        for i = 2 to n
+            if p[i] < 0 and (abs(p[i]) > abs(p[i-1])) and (abs(p[i]) > abs(p[k])) then k = i
+        next i
+        for i = 1 to n-1
+            if p[i] > 0 and (abs(p[i]) > abs(p[i+1])) and (abs(p[i]) > abs(p[k])) then k = i
+        next i
+        if k then
+            for i = 1 to n    #reverse elements > k
+                if abs(p[i]) > abs(p[k]) then p[i] = -p[i]
+            next i
+            if p[k] < 0 then i = k-1 else i = k+1
+            temp = p[k]
+            p[k] = p[i]
+            p[i] = temp
+            s = -s
+        end if
+    until k = 0
+end subroutine