Data commit

Task/Topswops/Go/topswops.go

@@ -0,0 +1,55 @@
+// Adapted from http://www-cs-faculty.stanford.edu/~uno/programs/topswops.w
+// at Donald Knuth's web site.  Algorithm credited there to Pepperdine
+// and referenced to Mathematical Gazette 73 (1989), 131-133.
+package main
+
+import "fmt"
+
+const ( // array sizes
+    maxn = 10 // max number of cards
+    maxl = 50 // upper bound for number of steps
+)
+
+func main() {
+    for i := 1; i <= maxn; i++ {
+        fmt.Printf("%d: %d\n", i, steps(i))
+    }
+}
+
+func steps(n int) int {
+    var a, b [maxl][maxn + 1]int
+    var x [maxl]int
+    a[0][0] = 1
+    var m int
+    for l := 0; ; {
+        x[l]++
+        k := int(x[l])
+        if k >= n {
+            if l <= 0 {
+                break
+            }
+            l--
+            continue
+        }
+        if a[l][k] == 0 {
+            if b[l][k+1] != 0 {
+                continue
+            }
+        } else if a[l][k] != k+1 {
+            continue
+        }
+        a[l+1] = a[l]
+        for j := 1; j <= k; j++ {
+            a[l+1][j] = a[l][k-j]
+        }
+        b[l+1] = b[l]
+        a[l+1][0] = k + 1
+        b[l+1][k+1] = 1
+        if l > m-1 {
+            m = l + 1
+        }
+        l++
+        x[l] = 0
+    }
+    return m
+}