Data update

Task/Permutations/AWK/permutations-2.awk

@@ -0,0 +1,33 @@
+# determine and print all permutations of numbers 1..n
+
+# General variant: simple, single array, recursive, not in lexical order
+#
+# An array with n places is used, marked by 0 as free.
+# The current element l replaces the free places one by one,
+# and the next element l+1 is probed recursively with the array.
+#
+function permute1(l, n, r,   i) {
+  if ( l <= n) {
+    for (i=1; i<=n; ++i) {
+      if (r[i] == 0) {
+        r[i] = l
+        permute1(l+1, n, r)
+        r[i] = 0
+      }
+    }
+    return
+  }
+  # print result; consumes ca. 50% of CPU time
+  s = ""
+  for (i=1; i <= length(r); ++i)  # ensure order
+    s = s r[i] " "
+  print s
+}
+
+# command line parameter is number of elements.
+BEGIN {
+  n = 3                               # default
+  if (ARGC > 1) n = ARGV[1]           # number may be given as parameter
+  for (i=1; i <=n; ++i) r[i] = 0      # fill with zeroes
+  permute1(1, n,  r)
+}

Task/Permutations/AWK/permutations-3.awk

@@ -0,0 +1,23 @@
+function permute(l, k,   i, s) {
+  if (k == length(l)) {
+    show(s)
+    return
+  }
+  for (i=k; i <= length(l); ++i) {
+    swap(l, i, k)
+    permute(l, k+1)
+    swap(l, k, i)
+  }
+}
+function swap(l, i, k,    t) {
+  t = l[i]
+  l[i] = l[k]
+  l[k] = t
+}
+BEGIN {
+  n = 3                               # default
+  if (ARGC > 1) n = ARGV[1]           # number may be given as parameter
+  for (i=1; i <=n; ++i)
+    l[i] = i
+  permute(l, 1)
+  }