Implement efficient algorithm in TF

Author: bertptrs

2024/bonus/day11/main.tf

@@ -4,12 +4,15 @@ variable "input" {
 
 locals {
   nums = [for s in split(" ", chomp(var.input)) : tonumber(s)]
+
+  grouped = { for num in local.nums : num => 1... }
+  total   = { for k, v in local.grouped : k => sum(v) }
 }
 
 module "step1" {
   source = "./step"
 
-  prev = local.nums
+  prev = local.total
 }
 
 module "step2" {
@@ -157,5 +160,5 @@ module "step25" {
 }
 
 output "part1" {
-  value = length(flatten(module.step25.next))
+  value = sum(values(module.step25.next))
 }

2024/bonus/day11/step/main.tf

@@ -1,14 +1,21 @@
 variable "prev" {
-  type = list(number)
+  type = map(number)
+}
+
+module "transform" {
+  source   = "../transform"
+  for_each = var.prev
+
+  num = each.key
 }
 
 locals {
-  values = [
-    for num in var.prev : num == 0 ? [1]
-    : length(tostring(num)) % 2 == 0
-    ? [tonumber(substr(tostring(num), 0, length(tostring(num)) / 2)), tonumber(substr(tostring(num), length(tostring(num)) / 2, 10))]
-    : [num * 2024]
-  ]
+  by_value = flatten([
+    for key, value in module.transform :
+    [for result in value.result : { num = result, count = var.prev[key] }]
+  ])
+
+  grouped = { for kv in local.by_value : kv.num => kv.count... }
 }
 
 # module "transform" {
@@ -23,5 +30,5 @@ locals {
 # }
 
 output "next" {
-  value = flatten(local.values)
+  value = { for num, groups in local.grouped : num => sum(groups) }
 }