Data commit

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

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+# Return the list L after applying Knuth shuffle. GAP also has the function Shuffle, which does the same.
+ShuffleAlt := function(a)
+    local i, j, n, t;
+    n := Length(a);
+    for i in [n, n - 1 .. 2] do
+        j := Random(1, i);
+        t := a[i];
+        a[i] := a[j];
+        a[j] := t;
+    od;
+    return a;
+end;
+
+# Return a "Permutation" object (a permutation of 1 .. n).
+# They are printed in GAP, in cycle decomposition form.
+PermShuffle := n -> PermList(ShuffleAlt([1 .. n]));
+
+ShuffleAlt([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)