Initial commit

21.jl

@@ -0,0 +1,70 @@
+function make_dice(max_value)
+    next = max_value - 1
+    r = 0
+    function roll()
+        r += 1
+        next += 1
+        next %= max_value
+        return next + 1
+    end
+    function rolls()
+        r
+    end
+    roll, rolls
+end
+
+function advance(pos, dice)
+    pos += dice()+dice()+dice()
+    ((pos - 1) % 10) + 1
+end
+
+function solution21_1()
+    pos_a = 8
+    pos_b = 5
+    dice, times = make_dice(100)
+    score_a = 0
+    score_b = 0
+    while true
+        pos_a = advance(pos_a, dice)
+        score_a += pos_a
+        println("a -> $pos_a ($score_a)")
+        if score_a >= 1000
+            r = times()
+            println("$score_b $r $(score_b * r)")
+            break
+        end
+        pos_b = advance(pos_b, dice)
+        score_b += pos_b
+        println("b -> $pos_b ($score_b)")
+        if score_b >= 1000
+            r = times()
+            println("$score_a $r $(score_a * r)")
+            break
+        end
+    end
+end
+
+using Pkg
+Pkg.add("Memoize")
+using Memoize
+
+DICE = [(a,b,c) for a in 1:3 for b in 1:3 for c in 1:3]
+
+@memoize function round(pa, pb, sa, sb)
+    sum(map(DICE) do dice
+            npa = pa + sum(dice)
+            npa = ((npa - 1) % 10) + 1
+            nsa = sa + npa
+            if nsa >= 21
+                [1, 0]
+            else
+                circshift(round(pb, npa, sb, nsa), 1)
+            end
+        end)
+end
+
+function solution21_2()
+    round(8, 5, 0, 0)
+end
+
+solution21_2()