[rs] 2023:01: Re-write part1; also solve part2

Author: kiriDevs

2023/day01/day01.rs

@@ -0,0 +1,95 @@
+use std::fs;
+use std::convert::TryInto;
+use std::str::Chars;
+use std::iter::Rev;
+
+enum CharIter<'a> {
+    Forward(Chars<'a>),
+    Backward(Rev<Chars<'a>>)
+}
+
+impl<'a> Iterator for CharIter<'a> {
+    type Item = char;
+    fn next(&mut self) -> Option<Self::Item> {
+        match self {
+            CharIter::Forward(itr) => itr.next(),
+            CharIter::Backward(itr) => itr.next(),
+        }
+    }
+}
+
+const TEXT_DIGITS: [(&str, u8); 10] = [
+    ("zero", 0), ("one", 1), ("two", 2), ("three", 3), ("four", 4),
+    ("five", 5), ("six", 6), ("seven", 7), ("eight", 8), ("nine", 9)
+];
+
+fn read_input(filename: &str) -> Vec<String> {
+    if let Ok(input_text) = fs::read_to_string(filename) {
+        input_text
+            .trim()
+            .split("\n")
+            .map(|line| line.trim().to_owned())
+            .collect()
+    } else {
+        panic!("Unable to read input from file: {}", filename);
+    }
+}
+
+fn get_text_digit(text: &str) -> Option<u8> {
+    for text_digit in TEXT_DIGITS {
+        if text.ends_with(text_digit.0) || text.starts_with(text_digit.0) {
+            return Some(text_digit.1);
+        }
+    }
+    None
+}
+
+fn _get_first_digit(chars: CharIter, convert_text: bool, reversed: bool) -> u8 {
+    let mut charbuf: String = String::new();
+
+    for char in chars {
+        if let Some(digit) = char.to_digit(10) {
+            return digit.try_into().unwrap();
+        }
+
+        if reversed { charbuf.insert(0, char); }
+        else { charbuf.push(char); }
+        if convert_text {
+            if let Some(text_digit) = get_text_digit(&charbuf) {
+                return text_digit;
+            }
+        }
+    }
+    panic!("Line does not have a digit!");
+}
+
+fn get_first_digit(line: &str, convert_text: bool) -> u8 {
+    _get_first_digit(CharIter::Forward(line.chars()), convert_text, false)
+}
+
+fn get_last_digit(line: &str, convert_text: bool) -> u8 {
+    _get_first_digit(CharIter::Backward(line.chars().rev()).into_iter(), convert_text, true)
+}
+
+fn get_digits(line: &str, convert_text: bool) -> (u8, u8) {
+    (get_first_digit(line, convert_text), get_last_digit(line, convert_text))
+}
+
+fn get_calibration_value((digit1, digit2): (u8, u8)) -> u8 {
+    format!("{digit1}{digit2}").parse().unwrap()
+}
+
+fn find_solution(lines: Vec<String>, convert_text: bool) -> usize {
+    lines.iter()
+        .map(|line| get_digits(line, convert_text))
+        .map(get_calibration_value)
+        .fold(0, |acc, calibration_value| {
+            acc + usize::from(calibration_value)
+        })
+}
+
+pub fn main() {
+    let input_lines: Vec<String> = read_input("input");
+    println!("Part 1: {}", find_solution(input_lines.clone(), false));
+    println!("Part 2: {}", find_solution(input_lines, true));
+}