From aeb6d67196f501f3c401e43bfa3d95fed1503e51 Mon Sep 17 00:00:00 2001
From: Greg Burri <greg.burri@gmail.com>
Date: Tue, 10 Dec 2024 21:03:10 +0100
Subject: [PATCH] More efficient matrix construction during data parsing

---
 src/day06.rs | 21 ++++++++++-----------
 src/day08.rs | 20 +++++++-------------
 2 files changed, 17 insertions(+), 24 deletions(-)

diff --git a/src/day06.rs b/src/day06.rs
index f027095..2f771be 100644
--- a/src/day06.rs
+++ b/src/day06.rs
@@ -7,26 +7,25 @@ type Pos = Point2<i32>;
 type Dir = Vector2<i32>;
 
 pub fn read_map(reader: &mut dyn BufRead) -> (Map, Pos) {
-    let mut map = DMatrix::default();
     let mut guard_position = Pos::default();
 
+    let mut data: Vec<bool> = Vec::new();
+    let mut nb_rows = 0;
+
     for (i, l) in reader.lines().enumerate() {
-        if map.nrows() < i + 1 {
-            map = map.insert_row(i, false);
-        }
+        nb_rows += 1;
         for (j, c) in l.unwrap().chars().enumerate() {
-            if map.ncols() < j + 1 {
-                map = map.insert_column(j, false);
-            }
-            if c == '#' {
-                map[(i, j)] = true;
-            } else if c == '^' {
+            data.push(c == '#');
+            if c == '^' {
                 guard_position = Pos::new(i as i32, j as i32);
             }
         }
     }
 
-    (map, guard_position)
+    (
+        Map::from_row_slice(nb_rows, data.len() / nb_rows, &data),
+        guard_position,
+    )
 }
 
 const ROT_MAT: Matrix2<i32> = Matrix2::new(0, 1, -1, 0);
diff --git a/src/day08.rs b/src/day08.rs
index 55d2816..00162ce 100644
--- a/src/day08.rs
+++ b/src/day08.rs
@@ -9,23 +9,17 @@ type Antinodes = DMatrix<bool>;
 const EMPTY: char = ' ';
 
 pub fn read(reader: &mut dyn BufRead) -> Antennae {
-    let mut antennae = Antennae::default();
+    let mut data: Vec<char> = Vec::new();
+    let mut nb_rows = 0;
 
-    for (i, l) in reader.lines().enumerate() {
-        if antennae.nrows() < i + 1 {
-            antennae = antennae.insert_row(i, EMPTY);
-        }
-        for (j, c) in l.unwrap().chars().enumerate() {
-            if antennae.ncols() < j + 1 {
-                antennae = antennae.insert_column(j, EMPTY);
-            }
-            if c != '.' {
-                antennae[(i, j)] = c;
-            }
+    for l in reader.lines() {
+        nb_rows += 1;
+        for c in l.unwrap().chars() {
+            data.push(if c == '.' { EMPTY } else { c });
         }
     }
 
-    antennae
+    Antennae::from_row_slice(nb_rows, data.len() / nb_rows, &data)
 }
 pub enum AntinodeMode {
     TwoPerPair,
-- 
2.45.2