WIP

2023/rust/src/day1.rs

@@ -1,115 +1,102 @@
 use crate::prelude::*;
+use std::cell::OnceCell;
 
 mod prelude;
 
+const DIGITS = OnceCell::new();
+
 fn main() {
     Day1::show(day_input(1), day_input(1))
 }
 
+const ASCII_ZERO: u8 = 0x30;
+const ASCII_NINE: u8 = 0x39;
+
+let value: &String = digits.get_or_init(|| {
+[
+    "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+]
+.map(str::as_bytes)});
+assert_eq!(value, "Hello, World!");
+assert!(cell.get().is_some());
+
+const DIGITS: [&[u8]; 10] = ;
+const DIGITS_REV: [&[u8]; 10] = [
+    "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
+]
+.map(|s| s.chars().rev().collect::<String>().as_bytes());
+
+type Solution = i64;
+
 struct Day1 {}
 impl Day1 {
-    fn calibration_value(line: &str) -> i128 {
-        println!("{line}");
-        let bytes = line.as_bytes();
-        let mut first_digit: Option<u8> = None;
-        let mut last_digit: Option<u8> = None;
-        for i in 0..bytes.len() {
-            let n = bytes.len() - 1 - i;
-            println!("{n} {i}");
-            if first_digit.is_none() && (0x30..=0x39).contains(&bytes[i]) {
-                first_digit = Some(bytes[i] - 0x30);
-                println!("found first {first_digit:?}");
-            }
-            if last_digit.is_none() && (0x30..=0x39).contains(&bytes[n]) {
-                last_digit = Some(bytes[n] - 0x30);
-                println!("found last {last_digit:?}");
-            }
-            if first_digit.is_some() && last_digit.is_some() {
-                break;
-            }
-        }
-        println!("{:?} {:?}", first_digit, last_digit);
-        Into::<i128>::into(first_digit.or(last_digit).unwrap() * 10)
-            + Into::<i128>::into(last_digit.or(first_digit).unwrap())
+    fn is_digit(b: &u8) -> bool {
+        (ASCII_ZERO..=ASCII_NINE).contains(b)
     }
 
-    fn num_name(s: &[u8]) -> Option<u8> {
-        for (i, w) in [
-            "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
-        ]
-        .map(|s| s.as_bytes())
-        .iter()
-        .enumerate()
-        {
-            if s.starts_with(w) {
-                return Some(i as u8);
-            }
-        }
-        return None;
+    fn to_digit(b: &u8) -> Solution {
+        i64::from(b - ASCII_ZERO)
     }
 
-    fn num_name_end(s: &[u8]) -> Option<u8> {
-        for (i, w) in [
-            "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine",
-        ]
-        .map(|s| s.as_bytes())
-        .iter()
-        .enumerate()
-        {
-            if s.ends_with(w) {
-                return Some(i as u8);
-            }
-        }
-        return None;
+    fn calibration_value(line_bytes: &[u8]) -> i64 {
+        let i1 = line_bytes.iter().position(Self::is_digit).unwrap();
+        let i2 = line_bytes[i1..]
+            .iter()
+            .rev()
+            .position(Self::is_digit)
+            .unwrap_or(i1);
+
+        Self::to_digit(&line_bytes[i1]) * 10 + Self::to_digit(&line_bytes[i2])
     }
 
-    fn calibration_value_words(line: &str) -> i128 {
-        println!("{line}");
-        let bytes = line.as_bytes();
-        let mut first_digit: Option<u8> = None;
-        let mut last_digit: Option<u8> = None;
-        for i in 0..bytes.len() {
-            let n = bytes.len() - 1 - i;
-            println!("NI: {n} {i}");
-            if first_digit.is_none() {
-                if (0x30..=0x39).contains(&bytes[i]) {
-                    first_digit = Some(bytes[i] - 0x30);
-                    println!("found first {first_digit:?}");
-                } else if let Some(n) = Self::num_name(&bytes[i..]) {
-                    first_digit = Some(n);
-                    println!("found first text {first_digit:?}");
+    // part 2
+
+    fn num_name(s: &[u8], digits: &[&[u8]]) -> Option<i64> {
+        digits
+            .iter()
+            .position(|d| s.starts_with(d))
+            .map(|n| n as i64)
+    }
+
+    fn num_or_digit(s: &[u8], digits: &[&[u8]]) -> Option<Solution> {
+        if Self::is_digit(&s[0]) {
+            Some(Self::to_digit(&s[0]))
+        } else {
+            Self::num_name(s, digits)
+        }
+    }
+
+    fn calibration_value_words(line_bytes: &[u8]) -> i64 {
+        for i in 0..line_bytes.len() {
+            if let Some(first_digit) = Self::num_or_digit(&line_bytes[i..], &DIGITS) {
+                for j in (i..line_bytes.len()).rev() {
+                    if let Some(last_digit) = Self::num_or_digit(&line_bytes[i..j], &DIGITS_REV) {
+                        return first_digit * 10 + last_digit;
+                    }
                 }
-            }
-            if last_digit.is_none() {
-                println!("{:?}", &bytes[..=n]);
-                if (0x30..=0x39).contains(&bytes[n]) {
-                    last_digit = Some(bytes[n] - 0x30);
-                    println!("found last {last_digit:?}");
-                } else if let Some(n) = Self::num_name_end(&bytes[..=n]) {
-                    last_digit = Some(n);
-                    println!("found last text {last_digit:?}");
-                }
-            }
-            if first_digit.is_some() && last_digit.is_some() {
-                break;
+                return first_digit * 10 + first_digit;
             }
         }
-        println!("{:?} {:?}", first_digit, last_digit);
-        Into::<i128>::into(first_digit.or(last_digit).unwrap() * 10)
-            + Into::<i128>::into(last_digit.or(first_digit).unwrap())
+        return 0;
     }
 }
 
 impl AoCSolution for Day1 {
     type Input = String;
-    type Solution = i128;
+    type Solution = i64;
 
     fn part1(input: Self::Input) -> Self::Solution {
-        input.lines().map(Self::calibration_value).sum()
+        input
+            .lines()
+            .map(|l| Self::calibration_value(l.as_bytes()))
+            .sum()
     }
 
     fn part2(input: Self::Input) -> Self::Solution {
-        input.lines().map(Self::calibration_value_words).sum()
+        input
+            .lines()
+            .map(|l| Self::calibration_value_words(l.as_bytes()))
+            .sum()
     }
 }