Add solutions for 2018 day 3.

2018/position.h

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+//
+// Created by Matthew Gretton-Dann on 14/12/2022.
+//
+
+#ifndef ADVENT_OF_CODE_POSITION_H
+#define ADVENT_OF_CODE_POSITION_H
+
+#include <compare>
+
+template<typename Int>
+struct Pos
+{
+  constexpr Pos() noexcept = default;
+  constexpr Pos(Int x, Int y) noexcept : x_(x), y_(y) {}
+  constexpr Pos(Pos const&) noexcept = default;
+  auto constexpr operator=(Pos const&) noexcept -> Pos& = default;
+  constexpr Pos(Pos&&) noexcept = default;
+  auto constexpr operator=(Pos&&) noexcept -> Pos& = default;
+  constexpr ~Pos() noexcept = default;
+
+  [[nodiscard]] auto constexpr x() const noexcept -> Int { return x_; }
+  auto constexpr x(Int x) noexcept { x_ = x; }
+  [[nodiscard]] auto constexpr y() const noexcept -> Int { return y_; }
+  auto constexpr y(Int y) noexcept { y_ = y; }
+
+  auto constexpr operator+=(Pos const& r) noexcept -> Pos&
+  {
+    x_ += r.x_;
+    y_ += r.y_;
+    return *this;
+  }
+
+  auto constexpr operator<=>(Pos const& r) const noexcept -> std::strong_ordering
+  {
+    auto result{y_ <=> r.y_};
+    if (result == std::strong_ordering::equal) {
+      result = x_ <=> r.x_;
+    }
+    return result;
+  }
+
+  auto constexpr operator==(Pos const& r) const noexcept -> bool
+  {
+    return x_ == r.x_ && y_ == r.y_;
+  }
+
+private:
+  Int x_{0};
+  Int y_{0};
+};
+
+template<typename Int>
+auto operator+(Pos<Int> const& x, Pos<Int> const& y) noexcept -> Pos<Int>
+{
+  auto z{x};
+  z += y;
+  return y;
+}
+
+#endif  // ADVENT_OF_CODE_POSITION_H

2018/puzzle-03-01.CMakeLists.txt

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+target_sources("${puzzle_name}" PRIVATE 2018/position.h)

2018/puzzle-03-01.cc

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+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <cstdlib>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "position.h"
+
+using Int = std::int64_t;
+
+struct Grid
+{
+  [[nodiscard]] auto width() const noexcept -> Int { return width_; }
+  [[nodiscard]] auto height() const noexcept -> Int { return static_cast<Int>(grid_.size()); }
+
+  auto add_rect(Pos<Int> tl, Pos<Int> br)
+  {
+    for (Int x{std::min(tl.x(), br.x())}; x < std::max(tl.x(), br.x()); ++x) {
+      for (Int y{std::min(tl.y(), br.y())}; y < std::max(tl.y(), br.y()); ++y) {
+        incr_point(Pos<Int>{x, y});
+      }
+    }
+  }
+
+  auto double_counted() const noexcept -> Int
+  {
+    Int result{0};
+    for (auto const& r : grid_) {
+      for (auto c : r) {
+        if (c > 1) {
+          ++result;
+        }
+      }
+    }
+    return result;
+  }
+
+private:
+  auto incr_point(Pos<Int> pos) -> void
+  {
+    auto const x{pos.x()};
+    auto const y{pos.y()};
+
+    if (y >= height()) {
+      grid_.resize(y + 1);
+    }
+    if (x >= grid_[y].size()) {
+      grid_[y].resize(x + 1, 0);
+      width_ = std::max(width_, x);
+    }
+    ++grid_[y][x];
+  }
+
+  std::vector<std::vector<Int>> grid_;
+  Int width_{0};
+};
+
+auto main() -> int
+{
+  std::string line;
+  Grid grid;
+
+  while (std::getline(std::cin, line)) {
+    assert(line[0] == '#');
+    std::size_t pos{1};
+    std::size_t l{0};
+    Int const id{std::stoll(line.substr(pos), &l)};
+    pos += l + 3;
+    Int const tlx{std::stoll(line.substr(pos), &l)};
+    pos += l + 1;
+    Int const tly{std::stoll(line.substr(pos), &l)};
+    pos += l + 2;
+    Int const w{std::stoll(line.substr(pos), &l)};
+    pos += l + 1;
+    Int const h{std::stoll(line.substr(pos), &l)};
+    grid.add_rect(Pos<Int>{tlx, tly}, Pos<Int>{tlx + w, tly + h});
+  }
+
+  std::cout << "Double counted: " << grid.double_counted() << '\n';
+
+  return EXIT_SUCCESS;
+}

2018/puzzle-03-02.CMakeLists.txt

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+target_sources("${puzzle_name}" PRIVATE 2018/position.h)

2018/puzzle-03-02.cc

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+//
+// Created by Matthew Gretton-Dann on 01/12/2022.
+//
+
+#include <cstdlib>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <set>
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "position.h"
+
+using Int = std::int64_t;
+
+struct Grid
+{
+  [[nodiscard]] auto width() const noexcept -> Int { return width_; }
+  [[nodiscard]] auto height() const noexcept -> Int { return static_cast<Int>(grid_.size()); }
+
+  auto add_rect(Pos<Int> tl, Pos<Int> br, Int value)
+  {
+    unique_.insert(value);
+    for (Int x{std::min(tl.x(), br.x())}; x < std::max(tl.x(), br.x()); ++x) {
+      for (Int y{std::min(tl.y(), br.y())}; y < std::max(tl.y(), br.y()); ++y) {
+        set_point(Pos<Int>{x, y}, value);
+      }
+    }
+  }
+
+  auto unique() const noexcept -> Int
+  {
+    assert(unique_.size() == 1);
+    return *unique_.begin();
+  }
+
+private:
+  auto set_point(Pos<Int> pos, Int value) -> void
+  {
+    auto const x{pos.x()};
+    auto const y{pos.y()};
+
+    if (y >= height()) {
+      grid_.resize(y + 1);
+    }
+    if (x >= grid_[y].size()) {
+      grid_[y].resize(x + 1, 0);
+      width_ = std::max(width_, x);
+    }
+    if (grid_[y][x] != 0) {
+      unique_.erase(grid_[y][x]);
+      unique_.erase(value);
+    }
+    grid_[y][x] = value;
+  }
+
+  std::vector<std::vector<Int>> grid_;
+  Int width_{0};
+  std::set<Int> unique_;
+};
+
+auto main() -> int
+{
+  std::string line;
+  Grid grid;
+
+  while (std::getline(std::cin, line)) {
+    assert(line[0] == '#');
+    std::size_t pos{1};
+    std::size_t l{0};
+    Int const id{std::stoll(line.substr(pos), &l)};
+    pos += l + 3;
+    Int const tlx{std::stoll(line.substr(pos), &l)};
+    pos += l + 1;
+    Int const tly{std::stoll(line.substr(pos), &l)};
+    pos += l + 2;
+    Int const w{std::stoll(line.substr(pos), &l)};
+    pos += l + 1;
+    Int const h{std::stoll(line.substr(pos), &l)};
+    grid.add_rect(Pos<Int>{tlx, tly}, Pos<Int>{tlx + w, tly + h}, id);
+  }
+
+  std::cout << "Unique: " << grid.unique() << '\n';
+
+  return EXIT_SUCCESS;
+}