2023 Day 13 Part 2

2023/puzzle-13-02.cc

@@ -0,0 +1,119 @@
+#include <cassert>
+#include <cstdint>
+#include <cstdlib>
+#include <iostream>
+#include <string>
+#include <vector>
+
+using UInt = std::uint64_t;
+
+auto has_smidge(std::string_view row1, std::string_view row2) -> bool
+{
+  assert(row1.size() == row2.size());
+  UInt diff_count{0};
+  for (auto it1{row1.begin()}, it2{row2.begin()}; it1 != row1.end(); ++it1, ++it2) {
+    diff_count += static_cast<UInt>(*it1 != *it2);
+  }
+  return diff_count == 1;
+}
+
+struct Grid
+{
+  void clear() { rows_.clear(); }
+  void push_back(std::string const& row) { rows_.push_back(row); }
+
+  [[nodiscard]] auto reflection_point(UInt const skip_row = 0) const -> UInt
+  {
+    for (std::size_t row{0}; row < rows_.size() - 1; ++row) {
+      if (row + 1 == skip_row) { continue; }
+      auto top{row};
+      auto bottom{row + 1};
+      while (rows_[top] == rows_[bottom]) {
+        if (top == 0 || bottom == rows_.size() - 1) { return row + 1; }
+        --top;
+        ++bottom;
+      }
+    }
+
+    return 0;
+  }
+
+  [[nodiscard]] auto find_smidge() const -> UInt
+  {
+    auto const skip_row{reflection_point()};
+
+    for (std::size_t row{0}; row < rows_.size() - 1; ++row) {
+      for (std::size_t row2{row + 1}; row2 < rows_.size(); ++row2) {
+        if (has_smidge(rows_[row], rows_[row2])) {
+          Grid temp(*this);
+          temp.rows_[row2] = temp.rows_[row];
+
+          if (auto const reflection_point = temp.reflection_point(skip_row);
+            reflection_point != 0) {
+            std::cout << "Found smidge between rows " << row << " and " << row2 << ". Score: " <<
+              reflection_point << " Skip row: " << skip_row << '\n';
+            for (std::size_t i{0}; i < rows_.size(); ++i) {
+              std::cout << rows_[i];
+              if (i == row || i == row2) { std::cout << " <<<"; }
+              std::cout << '\n';
+            }
+            return reflection_point;
+          }
+        }
+      }
+    }
+
+    std::cout << "No smidge point.\n";
+    return 0;
+  }
+
+  [[nodiscard]] auto rotate_right() const -> Grid
+  {
+    std::cout << "Rotate right\n";
+    Grid new_grid;
+    new_grid.rows_.resize(rows_.front().size());
+    for (auto row{rows_.rbegin()}; row != rows_.rend(); ++row) {
+      for (std::size_t i{0}; i < row->size(); ++i) {
+        new_grid.rows_[i].push_back(row->at(i));
+      }
+    }
+
+    return new_grid;
+  }
+
+private:
+  std::vector<std::string> rows_;
+};
+
+auto main() -> int try {
+  std::string line;
+
+  Grid grid;
+  UInt rows{0};
+  UInt cols{0};
+  while (std::getline(std::cin, line)) {
+    if (line.empty()) {
+      rows += grid.find_smidge();
+      grid = grid.rotate_right();
+      cols += grid.find_smidge();
+      grid.clear();
+      std::cout << "CLEAR\n";
+    }
+    else {
+      grid.push_back(line);
+    }
+  }
+
+  rows += grid.find_smidge();
+  grid = grid.rotate_right();
+  cols += grid.find_smidge();
+
+  std::cout << "Columns to left: " << cols << '\n' << "Rows above: " << rows << '\n' << "Score: " <<
+    cols + (rows * 100) << '\n';
+
+  return EXIT_SUCCESS;
+}
+catch (...) {
+  std::cerr << "Uncaught exception.\n";
+  return EXIT_FAILURE;
+}