Code tidy as reported by clang-tidy

main.cc

@@ -1,6 +1,6 @@
 /** \file main.cc
  *  \author Matthew Gretton-Dann
- *  \brief Solves the partirige problem for user specified size.
+ *  \brief Solves the Partridge problem for user specified size.
  *
  * Copyright 2025, Matthew-Gretton-Dann
  * SPDX: Apache-2.0
@@ -11,13 +11,12 @@
 #include <string_view>
 #include <vector>
 #include <iostream>
-#include <set>
-
-using size_t = std::size_t;
 
 namespace {
+  using size_t = std::uint64_t;
+
   /** (x, y) pair storing a position. */
-  using Pos = std::size_t;
+  using Pos = size_t;
 
   /** A square - consisting of position of closest corner to origin, and side-length.
    */
@@ -40,10 +39,10 @@ namespace {
     ~Square() noexcept = default;
 
     /** Get x co-ordinate of closest corner to origin. */
-    auto pos() const noexcept -> Pos { return pos_; }
+    [[nodiscard]] auto pos() const noexcept -> Pos { return pos_; }
 
     /** Get side length. */
-    auto length() const noexcept -> size_t { return length_; }
+    [[nodiscard]] auto length() const noexcept -> size_t { return length_; }
 
   private:
     Pos pos_; ///< Position of corner closest to origin
@@ -66,7 +65,7 @@ namespace {
 
     ~Results() noexcept = default;
 
-    auto length() const noexcept -> size_t { return length_; }
+    [[nodiscard]] auto length() const noexcept -> size_t { return length_; }
 
     /** Output the grid. */
     auto output() const -> void {
@@ -87,8 +86,8 @@ namespace {
       s[x + y * length_] = c;
     }
 
-    auto sq_x(Square const &sq) const noexcept -> size_t { return sq.pos() % length_; }
+    [[nodiscard]] auto sq_x(Square const &sq) const noexcept -> size_t { return sq.pos() % length_; }
-    auto sq_y(Square const &sq) const noexcept -> size_t { return sq.pos() / length_; }
+    [[nodiscard]] auto sq_y(Square const &sq) const noexcept -> size_t { return sq.pos() / length_; }
 
     auto prettify_sq(std::string &s, Square const &sq) const noexcept -> void {
       switch (sq.length()) {
@@ -117,7 +116,7 @@ namespace {
 
           size_t i = sq_x(sq) + n - 1;
           while (n != 0) {
-            set(s, --i, sq_y(sq) + 1, '0' + (n % 10));
+            set(s, --i, sq_y(sq) + 1, static_cast<char>('0' + static_cast<char>(n % 10)));
             n /= 10;
           }
         }
@@ -134,7 +133,7 @@ namespace {
     using T = std::int_fast64_t;
 
     /** Construct a grid of given side-length. */
-    Grid(size_t length) : grid_(length * length, empty), length_(length) {
+    explicit Grid(size_t length) : grid_(length * length, empty), length_(length) {
     }
 
     Grid(Grid const &other) = delete;
@@ -148,12 +147,12 @@ namespace {
     ~Grid() noexcept = default;
 
     /** Get grid length */
-    auto end() const noexcept -> size_t { return grid_.size(); }
+    [[nodiscard]] auto end() const noexcept -> size_t { return static_cast<size_t>(grid_.size()); }
 
     /** Add a square to the grid. */
     auto add(Square const &sq) noexcept -> void {
       /* One would expect the fastest way to do this would be to have x be the
-       * fastest increasing index so we stores [pos, pos + 1,..., pos+length, ...]
+       * fastest increasing index so we store [pos, pos + 1,..., pos+length, ...]
        * But experimentation tells us this isn't so, and storing
        * [pos, pos + length, ..., pos + 1, ...] is faster!
        */
@@ -175,7 +174,7 @@ namespace {
 
     /** \brief Get length of the largest square that fits at \a pos in the grid.
      */
-    auto largest_square(Pos pos, size_t n) const noexcept -> size_t {
+    [[nodiscard]] auto largest_square(Pos pos, size_t n) const noexcept -> size_t {
       assert(pos < end());
 
       /* Because of how we walk through the grid (starting at 0,0 then increasing
@@ -203,27 +202,15 @@ namespace {
 
     /** Get the next position to check starting at pos.
      *
-     * Returns grid_.length() if no more positions avaialble.
+     * Returns grid_.length() if no more positions available.
      */
-    auto next_pos(Pos pos) const noexcept -> Pos {
+    [[nodiscard]] auto next_pos(Pos pos) const noexcept -> Pos {
-      auto const b = grid_.begin() + pos;
+      auto const b = grid_.begin() + static_cast<std::ptrdiff_t>(pos);
       auto const p = std::find(b, grid_.end(), empty);
       return p - grid_.begin();
     }
 
   private:
-    /** Set the grid position (x, y) to the character c.
-     *
-     * It is an error if (x, y) is already set to c - as that means we have overlapping
-     * squares.
-     */
-    auto set(size_t x, size_t y, T c) noexcept -> void {
-      assert(x < length_);
-      assert(y < length_);
-      assert(grid_[x + y * length_] != c);
-      grid_[x + y * length_] = c;
-    }
-
     std::vector<T> grid_; ///< The grid
     size_t length_; ///< Side length
 
@@ -231,7 +218,7 @@ namespace {
     static constexpr char filled = 1; ///< Character used for a filled cell,
   };
 
-  /** Get the n'th triangular number. */
+  /** Get the n-th triangular number. */
   auto triangle_num(size_t n) noexcept -> size_t { return (n * (n + 1)) / 2; }
 
   /** Vector used to identify the available squares. */
@@ -253,7 +240,7 @@ namespace {
      * available squares until we find one that fits.
      */
 
-    // grid is our inprogress grid of square positions.
+    // grid is our in-progress grid of square positions.
     auto const length = triangle_num(n);
     Grid grid(length);
 
@@ -276,7 +263,7 @@ namespace {
     while (true) {
       /* If the idx is 0 we've looked at all possible square lengths for this
        * position, and they've failed.  Pop the last square of the stack, remove
-       * it from the grid and try the next smaller one in the same position.
+       * it from the grid and try the next smaller size in the same position.
        */
       if (idx == 0) {
         // No squares on the stack -> failed to find a solution.
@@ -312,13 +299,13 @@ namespace {
       if (pos == grid.end()) { break; }
     }
 
-    return Results(length, sqs);
+    return {length, sqs};
   }
 } // anon namespace
 
 int main(int argc, char **argv) {
   auto n = (argc == 1) ? 8 : std::atol(argv[1]);
-  auto grid = find_solution(n);
+  auto const grid = find_solution(n);
   std::cout << "Partridge problem " << n << " side length " << grid.length() << '\n';
   grid.output();
   return 0;