Data commit

Task/24-game-Solve/R/24-game-solve-1.r

@@ -0,0 +1,34 @@
+library(gtools)
+
+solve24 <- function(vals=c(8, 4, 2, 1),
+                    goal=24,
+                    ops=c("+", "-", "*", "/")) {
+
+  val.perms <- as.data.frame(t(
+                  permutations(length(vals), length(vals))))
+
+  nop <- length(vals)-1
+  op.perms <- as.data.frame(t(
+                  do.call(expand.grid,
+                          replicate(nop, list(ops)))))
+
+  ord.perms <- as.data.frame(t(
+                   do.call(expand.grid,
+                           replicate(n <- nop, 1:((n <<- n-1)+1)))))
+
+  for (val.perm in val.perms)
+    for (op.perm in op.perms)
+      for (ord.perm in ord.perms)
+        {
+          expr <- as.list(vals[val.perm])
+          for (i in 1:nop) {
+            expr[[ ord.perm[i] ]] <- call(as.character(op.perm[i]),
+                                          expr[[ ord.perm[i]   ]],
+                                          expr[[ ord.perm[i]+1 ]])
+            expr <- expr[ -(ord.perm[i]+1) ]
+          }
+          if (identical(eval(expr[[1]]), goal)) return(expr[[1]])
+        }
+
+  return(NA)
+}

Task/24-game-Solve/R/24-game-solve-2.r

@@ -0,0 +1,12 @@
+> solve24()
+8 * (4 - 2 + 1)
+> solve24(c(6,7,9,5))
+6 + (7 - 5) * 9
+> solve24(c(8,8,8,8))
+[1] NA
+> solve24(goal=49) #different goal value
+8 * (4 + 2) + 1
+> solve24(goal=52) #no solution
+[1] NA
+> solve24(ops=c('-', '/')) #restricted set of operators
+(8 - 2)/(1/4)