langs a-z

Task/Knuths-algorithm-S/OCaml/knuths-algorithm-s.ocaml

@@ -0,0 +1,25 @@
+let s_of_n_creator n =
+  let i = ref 0
+  and sample = ref [| |] in
+  fun item ->
+    incr i;
+    if !i <= n then sample := Array.append [| item |] !sample
+    else if Random.int !i < n then !sample.(Random.int n) <- item;
+    !sample
+
+let test n items_set =
+  let s_of_n = s_of_n_creator n in
+  Array.fold_left (fun _ v -> s_of_n v) [| |] items_set
+
+let () =
+  Random.self_init();
+  let n = 3 in
+  let num_items = 10 in
+  let items_set = Array.init num_items (fun i -> i) in
+  let results = Array.create num_items 0 in
+  for i = 1 to 100_000 do
+    let res = test n items_set in
+    Array.iter (fun j -> results.(j) <- succ results.(j)) res
+  done;
+  Array.iter (Printf.printf " %d") results;
+  print_newline()

Task/Knuths-algorithm-S/Objective-C/knuths-algorithm-s.m

@@ -0,0 +1,35 @@
+#import <Foundation/Foundation.h>
+
+typedef NSArray *(^SOfN)(id);
+
+SOfN s_of_n_creator(int n) {
+  NSMutableArray *sample = [NSMutableArray arrayWithCapacity:n];
+  __block int i = 0;
+  return [[^(id item) {
+    i++;
+    if (i <= n) {
+      [sample addObject:item];
+    } else if (rand() % i < n) {
+      [sample replaceObjectAtIndex:rand() % n withObject:item];
+    }
+    return sample;
+  } copy] autorelease];
+}
+
+int main(int argc, const char *argv[]) {
+  NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
+
+  NSCountedSet *bin = [[NSCountedSet alloc] init];
+  for (int trial = 0; trial < 100000; trial++) {
+    SOfN s_of_n = s_of_n_creator(3);
+    NSArray *sample;
+    for (int i = 0; i < 10; i++)
+      sample = s_of_n([NSNumber numberWithInt:i]);
+    [bin addObjectsFromArray:sample];
+  }
+  NSLog(@"%@", bin);
+  [bin release];
+
+  [pool release];
+  return 0;
+}

Task/Knuths-algorithm-S/PARI-GP/knuths-algorithm-s.pari

@@ -0,0 +1,15 @@
+KnuthS(v,n)={
+  my(u=vector(n,i,i));
+  for(i=n+1,#v,
+    if(random(i)<n,u[random(n)+1]=i)
+  );
+  vecextract(v,u)
+};
+test()={
+  my(v=vector(10),t);
+  for(i=1,1e5,
+    t=KnuthS([0,1,2,3,4,5,6,7,8,9],3);
+    v[t[1]+1]++;v[t[2]+1]++;v[t[3]+1]++
+  );
+  v
+};

Task/Knuths-algorithm-S/Perl-6/knuths-algorithm-s.pl6

@@ -0,0 +1,28 @@
+sub s_of_n_creator($n) {
+    my @sample;
+    my $i = 0;
+    -> $item {
+        if ++$i <= $n {
+            push @sample, $item;
+        }
+        elsif $i.rand < $n {
+            @sample[$n.rand] = $item;
+        }
+        @sample;
+    }
+}
+
+my @items = 0..9;
+my @bin;
+
+for ^100000 {
+    my &s_of_n = s_of_n_creator(3);
+    my @sample;
+    for @items -> $item {
+        @sample = s_of_n($item);
+    }
+    for @sample -> $s {
+        @bin[$s]++;
+    }
+}
+say @bin;