Data commit

Task/Knuth-shuffle/R/knuth-shuffle-1.r

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+fisheryatesshuffle <- function(n)
+{
+  pool <- seq_len(n)
+  a <- c()
+  while(length(pool) > 0)
+  {
+     k <- sample.int(length(pool), 1)
+     a <- c(a, pool[k])
+     pool <- pool[-k]
+  }
+  a
+}

Task/Knuth-shuffle/R/knuth-shuffle-2.r

@@ -0,0 +1,21 @@
+fisheryatesknuthshuffle <- function(n)
+{
+   a <- seq_len(n)
+   while(n >=2)
+   {
+      k <- sample.int(n, 1)
+      if(k != n)
+      {
+         temp <- a[k]
+         a[k] <- a[n]
+         a[n] <- temp
+      }
+      n <- n - 1
+   }
+   a
+}
+
+#Example usage:
+fisheryatesshuffle(6)                # e.g. 1 3 6 2 4 5
+x <- c("foo", "bar", "baz", "quux")
+x[fisheryatesknuthshuffle(4)]        # e.g. "bar"  "baz"  "quux" "foo"

Task/Knuth-shuffle/R/knuth-shuffle-3.r

@@ -0,0 +1,19 @@
+knuth <- function(vec)
+{
+  last <- length(vec)
+  if(last >= 2)
+  {
+    for(i in last:2)
+    {
+      j <- sample(seq_len(i), size = 1)
+      vec[c(i, j)] <- vec[c(j, i)]
+    }
+  }
+  vec
+}
+#Demonstration:
+knuth(integer(0))
+knuth(c(10))
+replicate(10, knuth(c(10, 20)))
+replicate(10, knuth(c(10, 20, 30)))
+knuth(c("Also", "works", "for", "strings"))