From a066fdb5524312c8efa294b97eba3abbf4d49c7a Mon Sep 17 00:00:00 2001
From: Matthew Gretton-Dann <matt@gretton-dann.org.uk>
Date: Thu, 4 Sep 2025 11:02:54 +0200
Subject: [PATCH] Convert Pos to an index.

Pos is now just an index into the grid.

This will be a slow down for the moment as we haven't worked through the
 changes to the algorithms yet.
---
 main.cc | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/main.cc b/main.cc
index 64e5ac8..3b4d80b 100644
--- a/main.cc
+++ b/main.cc
@@ -17,7 +17,7 @@ using size_t = std::size_t;
 
 namespace {
   /** (x, y) pair storing a position. */
-  using Pos = std::pair<size_t, size_t>;
+  using Pos = std::size_t;
 
   /** A square - consisting of position of closest corner to origin, and side-length.
    */
@@ -83,8 +83,8 @@ namespace {
       s[x + y * length_] = c;
     }
 
-    static auto sq_x(Square const& sq) noexcept -> size_t { return sq.pos().first; }
-    static auto sq_y(Square const& sq) noexcept -> size_t { return sq.pos().second; }
+     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_; }
 
     auto prettify_sq(std::string& s, Square const &sq) const noexcept -> void {
       switch (sq.length()) {
@@ -146,8 +146,8 @@ namespace {
     /** Get grid length */
     auto length() const noexcept -> size_t { return length_; }
 
-    auto pos_x(Pos const& pos) const noexcept -> size_t { return pos.first; }
-    auto pos_y(Pos const& pos) const noexcept -> size_t { return pos.second; }
+    auto pos_x(Pos const& pos) const noexcept -> size_t { return pos % length_; }
+    auto pos_y(Pos const& pos) const noexcept -> size_t { return pos / length_; }
 
     /** Add a square to the grid. */
     auto add(Square const &sq) noexcept -> void {
@@ -200,7 +200,7 @@ namespace {
       auto const b = grid_.begin() + pos_x(pos) + n + pos_y(pos) * length_;
       auto const p = std::find(b, grid_.end(), empty);
       auto const v = p - grid_.begin();
-      return std::make_pair(v % length_, v / length_);
+      return v;
     }
 
   private:
@@ -262,7 +262,7 @@ namespace {
     sqs.reserve(length);
 
     // Start at the origin with a square of longest side length.
-    Pos pos{0, 0};
+    Pos pos = 0;
     size_t idx = n;
 
     while (true) {