day 13

day13/Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day13"
+version = "0.1.0"

day13/Cargo.toml

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+[package]
+name = "day13"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day13/src/main.rs

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+use std::fs::read_to_string;
+use std::iter;
+use std::cmp;
+use std::time::Instant;
+
+fn encode_mirror_row(row: &[u8]) -> u32 {
+    let mut result: u32 = 0;
+    for &c in row {
+        result = (result << 1) | (c as u32 & 1);
+        // match c {
+        //     b'#' => result = (result << 1) | 1,
+        //     _ => result = result << 1
+        // }
+    }
+    result
+}
+
+fn encode_mirror_col(rows: &Vec<&[u8]>, index: usize) -> u32 {
+    let mut result = 0;
+    for &row in rows {
+        result = (result << 1) | (row[index] as u32 & 1);
+        // match row[index] {
+        //     b'#' => result = (result << 1) | 1,
+        //     _ => result = result << 1
+        // }
+    }
+    result
+}
+
+fn test_mirror_dim(mirror_dim: &Vec<u32>, index: usize) -> bool {
+    let span = cmp::min(index, mirror_dim.len() - index);
+    for i in 0..span {
+        if mirror_dim[index - i - 1] != mirror_dim[index + i] {
+            return false;
+        }
+    }
+    return true;
+}
+
+fn test_mirror_dim_smudge(mirror_dim: &Vec<u32>, index: usize) -> bool {
+    let span = cmp::min(index, mirror_dim.len() - index);
+    let mut num_errors = 0;
+    for i in 0..span {
+        let diff = mirror_dim[index - i - 1] ^ mirror_dim[index + i];
+        num_errors += u32::count_ones(diff)
+    }
+    num_errors == 1
+}
+
+fn solution(input_str: &str) -> (u32, u32) {
+    let mut sum1 = 0;
+    let mut sum2 = 0;
+    let mut current_mirror: Vec<&[u8]> = vec![];
+    let mut current_mirror_rows: Vec<u32> = vec![];
+    let mut current_mirror_cols: Vec<u32> = vec![];
+    for line in input_str.lines().chain(iter::once("")) {
+        if !line.is_empty() {
+            let as_bytes = line.as_bytes();
+            current_mirror.push(as_bytes);
+            current_mirror_rows.push(encode_mirror_row(as_bytes));
+        } else {
+            current_mirror_cols.extend((0..current_mirror[0].len()).map(
+                |index| encode_mirror_col(&current_mirror, index)
+            ));
+            // Task 1
+            let mut found = false;
+            for i in 1..current_mirror_rows.len() {
+                if test_mirror_dim(&current_mirror_rows, i) {
+                    sum1 += i as u32 * 100;
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                for i in 1..current_mirror_cols.len() {
+                    if test_mirror_dim(&current_mirror_cols, i) {
+                        sum1 += i as u32;
+                        break;
+                    }
+                }
+            }
+            // Task 2
+            found = false;
+            for i in 1..current_mirror_rows.len() {
+                if test_mirror_dim_smudge(&current_mirror_rows, i) {
+                    sum2 += i as u32 * 100;
+                    found = true;
+                    break;
+                }
+            }
+            if !found {
+                for i in 1..current_mirror_cols.len() {
+                    if test_mirror_dim_smudge(&current_mirror_cols, i) {
+                        sum2 += i as u32;
+                        break;
+                    }
+                }
+            }
+            current_mirror.clear();
+            current_mirror_rows.clear();
+            current_mirror_cols.clear();
+        }
+    }
+    (sum1, sum2)
+}
+
+fn main() {
+    let time_start = Instant::now();
+    let input_str = read_to_string("input.txt").unwrap();
+    let time_start_no_io = Instant::now();
+    let mut sum1 = 0;
+    let mut sum2 = 0;
+    // For performance measurement
+    for _ in 0..1 {
+        (sum1, sum2) = solution(&input_str);
+    }
+    let elapsed = time_start.elapsed().as_micros();
+    let elapsed_no_io = time_start_no_io.elapsed().as_micros();
+    println!("Time: {}us", elapsed);
+    println!("Time without file i/o: {}us", elapsed_no_io);
+    println!("Sum1: {}", sum1);
+    println!("Sum2: {}", sum2);
+}