From b9a91d78ab93c66964a964b0e8ae4cea3dd2b157 Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Sat, 5 Dec 2020 07:59:16 -0600
Subject: [PATCH] Naive day5 solution

---
 2020/src/aoc2020.nim    |  4 ++--
 2020/src/day5.nim       | 30 ++++++++++++++++++++++++++++++
 2020/src/day_loader.nim |  2 +-
 3 files changed, 33 insertions(+), 3 deletions(-)
 create mode 100644 2020/src/day5.nim

diff --git a/2020/src/aoc2020.nim b/2020/src/aoc2020.nim
index 720eab8..4d5052a 100644
--- a/2020/src/aoc2020.nim
+++ b/2020/src/aoc2020.nim
@@ -8,5 +8,5 @@ proc solve_for_day(n: int) {.used.} =
   echo solvers[n]()
 
 when isMainModule:
-  solve_all()
-  # solve_for_day(4)
+  # solve_all()
+  solve_for_day(5)
diff --git a/2020/src/day5.nim b/2020/src/day5.nim
new file mode 100644
index 0000000..31188ed
--- /dev/null
+++ b/2020/src/day5.nim
@@ -0,0 +1,30 @@
+import streams, bitops, sets
+
+# TODO: this one needs some refining for sure
+
+proc row(l: string): uint64 =
+  for c in l:
+    result = result.rotateLeftBits(1)
+    if c == 'B': result.setBit(0)
+
+proc col(l: string): uint64 =
+  for c in l:
+    result = result.rotateLeftBits(1)
+    if c == 'R': result.setBit(0)
+
+# do I really need row * 8 + col or can I just keep rotating and shifting
+proc toId(row: uint64, col: uint64): uint64 = (row*8)+col
+
+proc part1*(s: Stream): int =
+  for l in s.lines():
+    let id = cast[int](toId(row(l[0 .. 6]), col(l[7 .. ^1])))
+    if id > result: result = id
+
+proc part2*(s: Stream): int =
+  var ids = initHashSet[int]()
+  for l in s.lines():
+    let id = cast[int](toId(row(l[0 .. 6]), col(l[7 .. ^1])))
+    ids.incl(id)
+  for i in 1..890:
+    if ids.contains(i+1) and ids.contains(i-1) and not ids.contains(i):
+      return i
diff --git a/2020/src/day_loader.nim b/2020/src/day_loader.nim
index 05da3eb..e6fc2b4 100644
--- a/2020/src/day_loader.nim
+++ b/2020/src/day_loader.nim
@@ -3,7 +3,7 @@ import input_requestor, os, macros, strformat, tables
 macro loadDays(): untyped =
   var solver_str = "var solvers = {\n"
   result = newStmtList()
-  for day in 1..4:
+  for day in 1..5:
     let module = fmt"day{day}"
     if fileExists joinPath("src/", &"{module}.nim"):
       result.add parseStmt fmt"from {module} import nil"