From 849812d2e388b67ba08d8b30fbbb39711f93d864 Mon Sep 17 00:00:00 2001
From: Eric Mertens <emertens@gmail.com>
Date: Sun, 29 Dec 2024 09:33:33 -0600
Subject: [PATCH] 2024-01

---
 2024/01.cpp         | 54 +++++++++++++++++++++++++++++++++++++++++++++
 2024/CMakeLists.txt |  3 +++
 2 files changed, 57 insertions(+)
 create mode 100644 2024/01.cpp

diff --git a/2024/01.cpp b/2024/01.cpp
new file mode 100644
index 0000000..34f9c23
--- /dev/null
+++ b/2024/01.cpp
@@ -0,0 +1,54 @@
+#include <aocpp/Startup.hpp>
+
+#include <algorithm>
+#include <cstdint>
+#include <iostream>
+#include <vector>
+
+using std::find_if;
+using std::istream;
+using std::ostream;
+using std::size_t;
+using std::sort;
+using std::uint64_t;
+using std::vector;
+using std::distance;
+
+auto Main(istream & in, ostream & out) -> void
+{
+  vector<uint64_t> L1, L2;
+  {
+    uint64_t x, y;
+    while (in >> x >> y) {
+      L1.push_back(x);
+      L2.push_back(y);
+    }
+  }
+
+  sort(begin(L1), end(L1));
+  sort(begin(L2), end(L2));
+
+  uint64_t p1 = 0;
+  for (size_t i = 0; i < L1.size(); i++) {
+    p1 += L1[i] > L2[i] ? L1[i] - L2[i] : L2[i] - L1[i];
+  }
+
+  uint64_t p2 = 0;
+  for (auto i = begin(L1), j = begin(L2); i < end(L1) && j < end(L2); ) {
+    if (*i < *j) {
+      i++;
+    } else if (*j < *i) {
+      j++;
+    } else {
+      auto const p = [t = *i](auto const x) { return x != t; };
+      auto const i_ = find_if(i, end(L1), p);
+      auto const j_ = find_if(j, end(L2), p);
+      p2 += *i * (i_ - i) * (j_ - j);
+      i = i_;
+      j = j_;
+    }
+  }
+
+  out << "Part 1: " << p1 << "\n"
+      << "Part 2: " << p2 << "\n";
+}
diff --git a/2024/CMakeLists.txt b/2024/CMakeLists.txt
index 943266a..e4d52ec 100644
--- a/2024/CMakeLists.txt
+++ b/2024/CMakeLists.txt
@@ -1,3 +1,6 @@
+add_executable(2024_01 01.cpp)
+target_link_libraries(2024_01 aocpp Boost::headers)
+
 add_executable(2024_07 07.cpp)
 target_link_libraries(2024_07 aocpp Boost::headers)