Day 5

day_5/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "day_5"
+version = "0.1.0"
+authors = ["Smaug123 <patrick+github@patrickstevens.co.uk>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day_5/src/main.rs

@@ -0,0 +1,78 @@
+use std::convert::TryFrom;
+
+fn input() -> Vec<i32> {
+    let input = include_str!("../input.txt");
+    input
+        .lines()
+        .map(|l| {
+            l.parse()
+                .unwrap_or_else(|_| panic!("{} wasn't a valid u32", l))
+        })
+        .collect::<Vec<i32>>()
+}
+
+pub fn part_1(v: &mut Vec<i32>) -> u32 {
+    let mut count = 0;
+    let mut index: usize = 0;
+    while index < v.len() {
+        let bounce = v[index];
+        v[index] = bounce + 1;
+        let test = i32::try_from(index).unwrap() + bounce;
+        if test < 0 {
+            return count;
+        }
+        index = usize::try_from(test).unwrap();
+        count += 1;
+    }
+    count
+}
+
+pub fn part_2(v: &mut Vec<i32>) -> u32 {
+    let mut count = 0;
+    let mut index: usize = 0;
+    while index < v.len() {
+        let bounce = v[index];
+        if bounce >= 3 {
+            v[index] = bounce - 1;
+        } else {
+            v[index] = bounce + 1;
+        }
+        let test = i32::try_from(index).unwrap() + bounce;
+        if test < 0 {
+            return count;
+        }
+        index = usize::try_from(test).unwrap();
+        count += 1;
+    }
+    count
+}
+
+fn main() {
+    let input = input();
+    println!("part 1 => {}", part_1(&mut input.clone()));
+    let mut input = input;
+    println!("part 2 => {}", part_2(&mut input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn part1_known() {
+        assert_eq!(part_1(&mut vec![0, 3, 0, 1, -3]), 5);
+    }
+
+    #[test]
+    fn part2_known() {
+        assert_eq!(part_2(&mut vec![0, 3, 0, 1, -3]), 10);
+    }
+
+    #[test]
+    fn test_day_5() {
+        let input = input();
+        assert_eq!(part_1(&mut input.clone()), 391540);
+        let mut input = input;
+        assert_eq!(part_2(&mut input), 30513679);
+    }
+}