A-M baby

Task/Knuth-shuffle/GAP/knuth-shuffle.gap

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+# Return the list L after applying Knuth shuffle.
+Shuffle := function(L)
+  local i, j, n;
+  n := Length(L);
+  for i in [n, n-1 .. 1] do
+    j := Random(1, i);
+    x := L[i];
+    L[i] := L[j];
+    L[j] := x;
+  od;
+  return L;
+end;
+
+# Return a ''Permutation'' object (a permutation of 1..n).
+# They are printed in gap, in cycle decomposition form.
+PermShuffle := n -> PermListList([1 .. n], Shuffle([1 .. n]));
+
+Shuffle([1..10]);
+# [ 4, 7, 1, 5, 8, 2, 6, 9, 10, 3 ]
+PermShuffle(10);
+# (1,9)(2,3,6,4,5,10,8,7)
+
+# One may also call the built-in random generator on the symmetric group :
+Random(SymmetricGroup(10));
+(1,8,2,5,9,6)(3,4,10,7)