Time for an 2014 update…

Task/Set-puzzle/Go/set-puzzle.go

@@ -0,0 +1,85 @@
+package main
+
+import (
+    "fmt"
+    "math/rand"
+    "time"
+)
+
+var (
+    number = []string{"1", "2", "3"}
+    color  = []string{"red", "green", "purple"}
+    shade  = []string{"solid", "open", "striped"}
+    shape  = []string{"oval", "squiggle", "diamond"}
+)
+
+type card int
+
+func (c card) String() string {
+    return fmt.Sprintf("%s %s %s %s",
+        number[c/27],
+        color[c/9%3],
+        shade[c/3%3],
+        shape[c%3])
+}
+
+func main() {
+    rand.Seed(time.Now().Unix())
+    basic()
+    advanced()
+}
+
+func basic() {
+    game("Basic", 9, 4)
+}
+
+func advanced() {
+    game("Advanced", 12, 6)
+}
+
+func game(level string, cards, sets int) {
+    // create deck
+    d := make([]card, 81)
+    for i := range d {
+        d[i] = card(i)
+    }
+    var found [][3]card
+    for len(found) != sets {
+        found = found[:0]
+        // deal
+        for i := 0; i < cards; i++ {
+            j := rand.Intn(81 - i)
+            d[i], d[j] = d[j], d[i]
+        }
+        //  consider all triplets
+        for i := 2; i < cards; i++ {
+            c1 := d[i]
+            for j := 1; j < i; j++ {
+                c2 := d[j]
+            l3:
+                for _, c3 := range d[:j] {
+                    for f := card(1); f < 81; f *= 3 {
+                        if (c1/f%3+c2/f%3+c3/f%3)%3 != 0 {
+                            continue l3 // not a set
+                        }
+                    }
+                    // it's a set
+                    found = append(found, [3]card{c1, c2, c3})
+                }
+            }
+        }
+    }
+    // found the right number
+    fmt.Printf("%s game.  %d cards, %d sets.\n", level, cards, sets)
+    fmt.Println("Cards:")
+    for _, c := range d[:cards] {
+        fmt.Println("  ", c)
+    }
+    fmt.Println("Sets:")
+    for _, s := range found {
+        fmt.Println("  ", s[0])
+        fmt.Println("  ", s[1])
+        fmt.Println("  ", s[2])
+        fmt.Println()
+    }
+}