From 2439761d36a8757be8c89a3420707ba68b9c8252 Mon Sep 17 00:00:00 2001
From: Daniel Flanagan <daniel@lyte.dev>
Date: Thu, 3 Dec 2020 09:54:58 -0600
Subject: [PATCH] Day 2 implementation

---
 2020/src/aoc2020.nim       |  2 +-
 2020/src/day1.nim          | 13 ++++++-------
 2020/src/day2.nim          | 35 ++++++++++++++++++++++++++++++-----
 2020/src/day3.nim          |  7 +++++++
 2020/src/day_loader.nim    | 12 +++++++-----
 2020/src/input_helpers.nim |  9 +++++++++
 6 files changed, 60 insertions(+), 18 deletions(-)
 create mode 100644 2020/src/day3.nim
 create mode 100644 2020/src/input_helpers.nim

diff --git a/2020/src/aoc2020.nim b/2020/src/aoc2020.nim
index 814cd49..55a6b07 100644
--- a/2020/src/aoc2020.nim
+++ b/2020/src/aoc2020.nim
@@ -8,4 +8,4 @@ proc solve_for_day(n: int) {.used.} =
   echo solvers[n]()
 
 when isMainModule:
-  solve_for_day(2)
+  solve_all()
diff --git a/2020/src/day1.nim b/2020/src/day1.nim
index df28e2e..cfef733 100644
--- a/2020/src/day1.nim
+++ b/2020/src/day1.nim
@@ -1,19 +1,18 @@
-import sets, streams, strutils, options
+import sets, streams, strutils, options, input_helpers
 
 # Day 1
 
 let day1TargetSum = 2020
 
-proc part1*(strm: Stream): Option[int] =
+proc part1*(s: Stream): int =
   var targets = initHashSet[int]()
-  for line in strm.lines():
-    let n = parseInt line
+  for n in asInts(s):
     if targets.contains(day1TargetSum - n):
-      return some((day1TargetSum - n) * n)
+      return (day1TargetSum - n) * n
     else:
       targets.incl n
 
-proc part2*(strm: Stream): Option[int] =
+proc part2*(strm: Stream): int =
   # this works exactly the same as the previous algorithm, except we simply
   # permute once more
   # TODO: if I was really cool, I could split the shared functionality into
@@ -26,5 +25,5 @@ proc part2*(strm: Stream): Option[int] =
     let nTargetSum = day1TargetSum - n
     for n2 in nums:
       if iset.contains(nTargetSum - n2):
-        return some(n * n2 * (nTargetSum - n2))
+        return n * n2 * (nTargetSum - n2)
       iset.incl n2
diff --git a/2020/src/day2.nim b/2020/src/day2.nim
index e003789..080c3ec 100644
--- a/2020/src/day2.nim
+++ b/2020/src/day2.nim
@@ -1,7 +1,32 @@
-import streams
+import streams, strutils, sequtils, re, options
 
-proc part1*(strm: Stream): string =
-  "ayy"
+type PasswordPolicy = tuple[min: int, max: int, keyChar: char]
 
-proc part2*(strm: Stream): string =
-  "ayy"
+proc isValidPassword(str: string, pp: PasswordPolicy): bool =
+  let count = str.count pp.keyChar
+  (pp.min <= count) and (count <= pp.max)
+
+proc isValidPasswordPart2(str: string, pp: PasswordPolicy): bool =
+  (str[pp.min - 1] == pp.keyChar) xor (pp.keyChar == str[pp.max - 1])
+
+let parsePasswordPolicyRe = re"^(\d+)-(\d+) (.): (.*)$"
+proc parsePasswordPolicy(str: string): (PasswordPolicy, string) =
+  var matches: array[4, string]
+  if match(str, parsePasswordPolicyRe, matches):
+    return ((min: parseInt(matches[0]), max: parseInt(matches[1]), keyChar: matches[2][0]), matches[3])
+
+iterator asPasswordPolicies(s: Stream): (PasswordPolicy, string) =
+  for line in s.lines():
+    yield parsePasswordPolicy line
+
+proc part1*(s: Stream): int =
+  result = 0
+  for (pp, pw) in asPasswordPolicies(s):
+    if isValidPassword(pw, pp):
+      result += 1
+
+proc part2*(s: Stream): int =
+  result = 0
+  for (pp, pw) in asPasswordPolicies(s):
+    if isValidPasswordPart2(pw, pp):
+      result += 1
diff --git a/2020/src/day3.nim b/2020/src/day3.nim
new file mode 100644
index 0000000..7a4ee8f
--- /dev/null
+++ b/2020/src/day3.nim
@@ -0,0 +1,7 @@
+import streams
+
+proc part1*(s: Stream): int =
+  0
+
+proc part2*(s: Stream): int =
+  0
diff --git a/2020/src/day_loader.nim b/2020/src/day_loader.nim
index 6414b48..93c0b20 100644
--- a/2020/src/day_loader.nim
+++ b/2020/src/day_loader.nim
@@ -3,15 +3,17 @@ import input_requestor, os, macros, strformat, tables
 macro loadDays(): untyped =
   var solver_str = "var solvers = {\n"
   result = newStmtList()
-  for day in 1..2:
+  for day in 1..3:
     let module = fmt"day{day}"
     if fileExists joinPath("src/", &"{module}.nim"):
       result.add parseStmt fmt"from {module} import nil"
       solver_str = solver_str & &"""
-      {day}: proc(): (string, string) = (
-        $(day{day}.part1(getInputFileStreamForDay({day}))),
-        $(day{day}.part2(getInputFileStreamForDay({day})))
-      ),
+      {day}: proc(): tuple[part1: int, part2: int] =
+        echo "Day {day}"
+        (
+          {module}.part1(getInputFileStreamForDay({day})),
+          {module}.part2(getInputFileStreamForDay({day}))
+        ),
       """
   result.add parseStmt (solver_str & "\n}.newTable()\nexport solvers")
 
diff --git a/2020/src/input_helpers.nim b/2020/src/input_helpers.nim
new file mode 100644
index 0000000..41d6511
--- /dev/null
+++ b/2020/src/input_helpers.nim
@@ -0,0 +1,9 @@
+import streams, strutils, sugar
+
+iterator mapStream*[T](s: Stream, cb: (string) -> T): T =
+  for line in s.lines():
+    yield cb line
+
+iterator asInts*(s: Stream): int =
+  for i in mapStream[int](s, parseInt):
+    yield i