From ab86531dc591de07a15f51d735191e0503c74a09 Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@gmail.com>
Date: Mon, 4 Dec 2023 19:52:30 -0800
Subject: [PATCH] 2023-01

---
 2023/01.cpp         | 97 +++++++++++++++++++++++++++++++++++++++++++++
 2023/CMakeLists.txt |  3 ++
 2 files changed, 100 insertions(+)
 create mode 100644 2023/01.cpp

diff --git a/2023/01.cpp b/2023/01.cpp
new file mode 100644
index 0000000..20369ba
--- /dev/null
+++ b/2023/01.cpp
@@ -0,0 +1,97 @@
+#include <algorithm>
+#include <cctype>
+#include <cstdint>
+#include <iostream>
+#include <string_view>
+#include <string>
+#include <tuple>
+#include <tuple>
+#include <vector>
+
+#include <aocpp/Startup.hpp>
+
+namespace {
+
+using Input = std::vector<std::string>;
+
+/// @brief Parse the input stream as a newline-delimited list of lists of integers
+/// @param in input file parsed until EOF
+/// @return outer list of elves, inner lists of calories
+auto Parse(std::istream & in) -> Input
+{
+  Input results {};
+  std::move(
+    std::istream_iterator<std::string>{in},
+    std::istream_iterator<std::string>{},
+    std::back_inserter(results)
+  );
+  return results;
+}
+
+auto Part1(Input const& entries) -> std::int64_t
+{
+    std::int64_t acc = 0;
+    for (auto const& entry : entries)
+    {
+        auto lhs = std::find_if(entry.begin(),  entry.end(),  [](char c){ return std::isdigit(c); });
+        auto rhs = std::find_if(entry.rbegin(), entry.rend(), [](char c){ return std::isdigit(c); });
+        acc += 10 * (*lhs - '0') + (*rhs - '0');
+    }
+
+    return acc;
+}
+
+auto Part2(Input const& entries) -> std::int64_t
+{
+  static std::pair<char const*, std::int64_t> numbers[] = {
+    {"one", 1}, {"two", 2}, {"three", 3},
+    {"four", 4}, {"five", 5}, {"six", 6},
+    {"seven", 7}, {"eight", 8}, {"nine", 9},
+    {"0",0},{"1",1},{"2",2},{"3",3},{"4",4},
+    {"5",5},{"6",6},{"7",7},{"8",8},{"9",9}
+  };
+
+  std::int64_t acc = 0;
+  for (auto const& entry : entries)
+  {
+
+    std::int64_t lhs = 0;
+    std::int64_t rhs = 0;
+
+    for (auto cursor = entry.begin(); cursor < entry.end(); cursor++)
+    {
+      for (auto const [k,v] : numbers)
+      {
+        if (std::string_view{cursor, entry.end()}.starts_with(k)) {
+          lhs = v;
+          goto do_rhs;
+        }
+      }
+    }
+
+    do_rhs:
+    for (auto cursor = entry.end(); cursor --> entry.begin();)
+    {
+      std::int64_t lhs = 0;
+      for (auto const [k,v] : numbers)
+      {
+        if (std::string_view{cursor, entry.end()}.starts_with(k)) {
+          rhs = v;
+          goto next;
+        }
+      }
+    }
+    next:
+      acc += 10 * lhs + rhs;
+  }
+  return acc;
+}
+
+} // namespace
+
+auto Main(std::istream & in, std::ostream & out) -> void
+{
+  auto const entries = Parse(in);
+  out << "Part 1: " << Part1(entries) << std::endl;
+  out << "Part 2: " << Part2(entries) << std::endl;
+}
diff --git a/2023/CMakeLists.txt b/2023/CMakeLists.txt
index bff6a05..4617469 100644
--- a/2023/CMakeLists.txt
+++ b/2023/CMakeLists.txt
@@ -1,3 +1,6 @@
+add_executable(2023_01 01.cpp)
+target_link_libraries(2023_01 aocpp Boost::headers)
+
 add_executable(2023_02 02.cpp)
 target_link_libraries(2023_02 aocpp Boost::headers)