Data commit

Task/Permutations-by-swapping/Lua/permutations-by-swapping-1.lua

@@ -0,0 +1,41 @@
+_JT={}
+function JT(dim)
+  local n={ values={}, positions={}, directions={}, sign=1 }
+  setmetatable(n,{__index=_JT})
+  for i=1,dim do
+    n.values[i]=i
+    n.positions[i]=i
+    n.directions[i]=-1
+  end
+  return n
+end
+
+function _JT:largestMobile()
+  for i=#self.values,1,-1 do
+    local loc=self.positions[i]+self.directions[i]
+    if loc >= 1 and loc <= #self.values and self.values[loc] < i then
+      return i
+    end
+  end
+  return 0
+end
+
+function _JT:next()
+  local r=self:largestMobile()
+  if r==0 then return false end
+  local rloc=self.positions[r]
+  local lloc=rloc+self.directions[r]
+  local l=self.values[lloc]
+  self.values[lloc],self.values[rloc] = self.values[rloc],self.values[lloc]
+  self.positions[l],self.positions[r] = self.positions[r],self.positions[l]
+  self.sign=-self.sign
+  for i=r+1,#self.directions do self.directions[i]=-self.directions[i] end
+  return true
+end
+
+-- test
+
+perm=JT(4)
+repeat
+  print(unpack(perm.values))
+until not perm:next()

Task/Permutations-by-swapping/Lua/permutations-by-swapping-2.lua

@@ -0,0 +1,21 @@
+local wrap, yield = coroutine.wrap, coroutine.yield
+local function perm(n)
+    local r = {}
+    for i=1,n do r[i]=i end
+    local sign = 1
+  return wrap(function()
+    local function swap(m)
+      if m==0 then
+        sign = -sign, yield(sign,r)
+      else
+        for i=m,1,-1 do
+          r[i],r[m]=r[m],r[i]
+          swap(m-1)
+          r[i],r[m]=r[m],r[i]
+        end
+      end
+    end
+    swap(n)
+  end)
+end
+for sign,r in perm(3) do print(sign,table.unpack(r))end