From ab3eec6687e34e4473f720434d7de9c544f9fb5d Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Wed, 9 Dec 2020 09:37:54 -0600
Subject: [PATCH] Day 9! Code re-use!

---
 2020/src/aoc2020.nim |  5 +++--
 2020/src/day1.nim    |  3 ++-
 2020/src/day9.nim    | 37 +++++++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 3 deletions(-)
 create mode 100644 2020/src/day9.nim

diff --git a/2020/src/aoc2020.nim b/2020/src/aoc2020.nim
index 9a16381..2f29270 100644
--- a/2020/src/aoc2020.nim
+++ b/2020/src/aoc2020.nim
@@ -8,5 +8,6 @@ proc solve_for_day(n: int) {.used.} =
   echo solvers[n]()
 
 when isMainModule:
-  solve_all()
-  # solve_for_day(8)
+  # solve_all()
+  # solve_for_day(1)
+  solve_for_day(9)
diff --git a/2020/src/day1.nim b/2020/src/day1.nim
index 00a880d..1fa970f 100644
--- a/2020/src/day1.nim
+++ b/2020/src/day1.nim
@@ -2,8 +2,9 @@ import sets, streams, input_helpers, sequtils, options
 
 let targetSum = 2020
 
-proc findComplement(nums: seq[int], complement = targetSum): Option[(int, int)] =
+proc findComplement*(nums: openArray[int], complement = targetSum): Option[(int, int)] =
   var targets = initHashSet[int]()
+  echo nums
   for n in nums:
     if targets.contains(complement - n): return some(((complement - n), n))
     else: targets.incl n
diff --git a/2020/src/day9.nim b/2020/src/day9.nim
new file mode 100644
index 0000000..a8f71cd
--- /dev/null
+++ b/2020/src/day9.nim
@@ -0,0 +1,37 @@
+import streams, sequtils, sets, options, deques, input_helpers, day1
+
+const WINDOW = 25
+
+proc part1*(s: Stream): int =
+  var rollingWindow = initDeque[int](WINDOW)
+  for i in s.asInts:
+    echo i
+    if rollingWindow.len < WINDOW:
+      rollingWindow.addFirst(i)
+      continue
+    else:
+      let maybe = toSeq(rollingWindow).findComplement(i)
+      if maybe.isSome:
+        rollingWindow.addFirst(i)
+        rollingWindow.popLast
+      else: return i
+
+proc part2*(s: Stream): int =
+  let n = s.part1
+  s.setPosition 0
+  let nums = toSeq(s.asInts)
+  for i in 0..<nums.len:
+    var mn = n
+    var mx = 0
+    var sum = nums[i]
+    echo i, " i: ", nums[i]
+    mn = min(nums[i], mn)
+    mx = max(nums[i], mx)
+    for j in i+1..<nums.len:
+      echo j, " j: ", nums[j], " -- ", sum
+      mn = min(nums[j], mn)
+      mx = max(nums[j], mx)
+      if sum == n: return mn+mx
+      if sum > n: continue
+      sum += nums[j]
+