day13pt2: done

Author: tung

Cargo.lock

@@ -25,6 +25,7 @@ members = [
     "day12",
     "day12pt2",
     "day13",
+    "day13pt2",
 ]
 
 [profile.dev]

Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day13pt2"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day13pt2/Cargo.toml

@@ -0,0 +1,92 @@
+fn reflects_at_row(rows: &[String], r: usize) -> bool {
+    if r >= rows.len() - 1 {
+        return false;
+    }
+    let mut mismatches: usize = 0;
+    for i in 0..(r + 1).min(rows.len() - r - 1) {
+        let above = r - i;
+        let below = r + i + 1;
+        if rows[above] != rows[below] {
+            for (ca, cb) in rows[above].chars().zip(rows[below].chars()) {
+                if ca != cb {
+                    mismatches += 1;
+                }
+            }
+            if mismatches > 1 {
+                break;
+            }
+        }
+    }
+    mismatches == 1
+}
+
+fn transpose(rows: &[String]) -> Vec<String> {
+    let mut new_rows: Vec<String> = Vec::new();
+    let mut char_iters = rows
+        .iter()
+        .map(|s| s.chars())
+        .collect::<Vec<std::str::Chars>>();
+    loop {
+        let row = char_iters
+            .iter_mut()
+            .map(Iterator::next)
+            .flatten()
+            .collect::<String>();
+        if row == "" {
+            break;
+        } else {
+            new_rows.push(row);
+        }
+    }
+    new_rows
+}
+
+fn main() {
+    let mut maps: Vec<Vec<String>> = Vec::new();
+    let mut rows: Vec<String> = Vec::new();
+    for line in std::io::stdin().lines().map(Result::unwrap) {
+        if line.is_empty() && !rows.is_empty() {
+            maps.push(rows);
+            rows = Vec::new();
+        }
+        if !line.is_empty() {
+            rows.push(line.to_string());
+        }
+    }
+    if !rows.is_empty() {
+        maps.push(rows);
+    }
+
+    let sum = maps
+        .iter()
+        .map(|rows| {
+            let reflect_row = (0..rows.len())
+                .position(|r| reflects_at_row(rows, r))
+                .map(|r| r + 1)
+                .unwrap_or(0);
+            let t_rows = transpose(rows);
+            let reflect_column = (0..t_rows.len())
+                .position(|r| reflects_at_row(&t_rows, r))
+                .map(|r| r + 1)
+                .unwrap_or(0);
+            reflect_row * 100 + reflect_column
+        })
+        .sum::<usize>();
+    println!("{sum}");
+}
+
+#[test]
+#[rustfmt::skip]
+fn test_transpose() {
+    let input = &[
+        "###",
+        ".#.",
+        "...",
+    ].iter().map(|s| s.to_string()).collect::<Vec<String>>();
+    let expected = &[
+        "#..",
+        "##.",
+        "#..",
+    ].iter().map(|s| s.to_string()).collect::<Vec<String>>();
+    assert_eq!(expected, &transpose(&input));
+}