day 1

src/bin/day1.rs

@@ -0,0 +1,94 @@
+use aoc23::prelude::*;
+
+fn d1_0(input: String) -> Result<usize> {
+    let mut sum = 0;
+    for line in input.lines().into_iter() {
+        let chars = line.chars();
+        let first_num: usize = chars.clone().into_iter().skip_while(|c| !c.is_digit(10)).take(1)
+            // This would get continuous digits: .take_while(|c| c.is_digit(10))
+            .collect::<String>().parse()?;
+        let last_num: usize =
+            chars.into_iter().rev().skip_while(|c| !c.is_digit(10)).take(1).collect::<String>().parse()?;
+        let value = first_num * 10 + last_num;
+        sum += value;
+    }
+
+    // println!("Answer: {}", sum);
+    Ok(sum)
+}
+
+fn num_to_word(num: u32) -> Option<&'static str> {
+    match num {
+        1 => Some("one"),
+        2 => Some("two"),
+        3 => Some("three"),
+        4 => Some("four"),
+        5 => Some("five"),
+        6 => Some("six"),
+        7 => Some("seven"),
+        8 => Some("eight"),
+        9 => Some("nine"),
+        _ => None,
+    }
+}
+
+fn first_occurrence(str: &str, reversed: bool) -> Option<u32> {
+    if reversed {
+        for (i, char) in str.chars().rev().enumerate() {
+            let digit = char.to_digit(10).or_else(|| {
+                for num in 1 ..= 9 {
+                    if let Some(num_word) = num_to_word(num) {
+                        if i + 1 >= num_word.len() &&
+                            &str[str.len() - i - 1 .. str.len()][..num_word.len()] == num_word {
+                            return Some(num);
+                        }
+                    }
+                }
+                None
+            });
+            if digit.is_some() {
+                return digit;
+            }
+        }
+    } else {
+        for (i, char) in str.chars().enumerate() {
+            let digit = char.to_digit(10).or_else(|| {
+                for num in 1 ..= 9 {
+                    if let Some(num_word) = num_to_word(num) {
+                        if i + 1 >= num_word.len() && &str[i + 1 - num_word.len() ..= i] == num_word {
+                            return Some(num);
+                        }
+                    }
+                }
+                None
+            });
+            if digit.is_some() {
+                return digit;
+            }
+        }
+    }
+    None
+}
+
+fn d1_1(input: String) -> Result<u32> {
+    let mut sum = 0;
+    for line in input.lines().into_iter() {
+        let first_num = first_occurrence(line, false).ok_or("No number found in line")?;
+        let last_num = first_occurrence(line, true).ok_or("No number found in line reversed")?;
+        let value = first_num * 10 + last_num;
+        sum += value;
+    }
+
+    Ok(sum)
+}
+
+#[tokio::main]
+async fn main() -> Result<()> {
+    println!("Day 1");
+    println!("=====");
+    let input = utils::aoc::get_puzzle_input(1).await?;
+
+    println!("Day 1, 0: {}", d1_0(input.clone())?);
+    println!("Day 1, 1: {}", d1_1(input.clone())?);
+    Ok(())
+}