From 140dd1171538b1402d4918fc18a94995536ee9b4 Mon Sep 17 00:00:00 2001
From: Mars Ultor <krishna@ayyalasomayajula.net>
Date: Tue, 2 Dec 2025 00:35:58 -0600
Subject: [PATCH] part two tm

---
 src/day-2-solution.cpp | 90 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 90 insertions(+)
 create mode 100644 src/day-2-solution.cpp

diff --git a/src/day-2-solution.cpp b/src/day-2-solution.cpp
new file mode 100644
index 0000000..b95b51a
--- /dev/null
+++ b/src/day-2-solution.cpp
@@ -0,0 +1,90 @@
+
+#include "spdlog/common.h"
+#include "spdlog/fmt/bundled/format.h"
+#include "spdlog/spdlog.h"
+#include <cstddef>
+#include <cstdint>
+#include <exception>
+#include <fstream>
+#include <ios>
+#include <iterator>
+#include <string>
+#include <string_view>
+#include <utility>
+#include <vector>
+
+std::vector<std::pair<uint_fast64_t,uint_fast64_t>> parse_ranges(std::string_view input) {
+    std::vector<std::pair<uint_fast64_t,uint_fast64_t>> ranges;
+
+    size_t pos = 0;
+    while (pos < input.size()) {
+        // Find next '-' for the start-end split
+        size_t dash = input.find('-', pos);
+        if (dash == std::string_view::npos) break;
+
+        uint_fast64_t start;
+        auto [ptr1, ec1] = std::from_chars(input.data() + pos, input.data() + dash, start);
+        if (ec1 != std::errc()) break;
+
+        pos = dash + 1;
+
+        // Find next ',' for end of range
+        size_t comma = input.find(',', pos);
+        if (comma == std::string_view::npos) comma = input.size();
+
+        uint_fast64_t end;
+        auto [ptr2, ec2] = std::from_chars(input.data() + pos, input.data() + comma, end);
+        if (ec2 != std::errc()) break;
+
+        ranges.emplace_back(start, end);
+
+        pos = comma + 1; // move past comma
+    }
+
+    return ranges;
+}
+
+uint_fast64_t solution_part_one(std::vector<std::pair<uint_fast64_t, uint_fast64_t>> ranges ){
+  uint_fast64_t running_sum = uint_fast64_t{0};
+  for (std::vector<std::pair<uint_fast64_t, uint_fast64_t>>::const_iterator i =ranges.cbegin(); i<ranges.cend(); i++) {
+    spdlog::debug("range: {} to {}", i->first, i->second); 
+    for (uint_fast64_t j = i->first; j<= i->second; j++) {
+      std::string number = fmt::format("{}",j);
+      if(number.size()%2 ==1) continue;
+      
+      std::string::const_iterator start = number.cbegin();
+      std::string::const_iterator mid = number.cbegin()+number.size()/2;
+      std::string::const_iterator end = number.cend();
+
+      std::string_view first_half = std::string_view{&*start, static_cast<size_t>(mid-start)};
+      std::string_view second_half = std::string_view{&*mid, static_cast<size_t>(end-mid)};
+
+      if(first_half==second_half) running_sum+=j;
+    }
+  }
+  return running_sum;
+}
+
+
+int main (int argc, char *argv[]) {
+  spdlog::set_level(spdlog::level::level_enum::debug);
+  
+  std::ifstream input = std::ifstream{"testcases/day-2.in", std::ios_base::binary | std::ios::ate};
+  
+  std::streamsize size_of_buffer = input.tellg();
+  input.seekg(0, std::ios::beg);
+
+  std::string loaded_buffer = std::string(static_cast<size_t>(size_of_buffer), '\0'); 
+
+  if(!input.read(loaded_buffer.data(),size_of_buffer)) {
+    spdlog::critical("Read error"); std::terminate();
+  }
+
+  std::vector<std::pair<uint_fast64_t, uint_fast64_t>> ranges = parse_ranges(loaded_buffer);
+  spdlog::debug("Size of ranges: {}", ranges.size());
+  uint_fast64_t first_part_response = solution_part_one(ranges);
+  spdlog::info("Solution to part one: {}", first_part_response);
+
+
+  return 0;
+}