Day 5 Alchemical Reduction

src/aoc/c05.rs

@@ -0,0 +1,93 @@
+pub fn run(input: &[&str], part: u8) -> String {
+    match part {
+        1 => c_05_1(input[0]).to_string(),
+        2 => c_05_2(input[0]).to_string(),
+        _ => panic!("unknown part"),
+    }
+}
+
+fn c_05_1(input: &str) -> i32 {
+    let mut stack: Vec<u8> = Vec::with_capacity(input.len());
+
+    for c in input.chars() {
+        let b = c as u8;
+        match stack.pop() {
+            Some(v) => {
+                if v != b + 0x20 && v != b - 0x20 {
+                    stack.push(v);
+                    stack.push(b);
+                }
+            }
+            None => stack.push(b),
+        };
+    }
+
+    stack.len() as i32
+}
+
+fn c_05_2(input: &str) -> i32 {
+    let mut stack: Vec<u8> = Vec::with_capacity(input.len());
+    let mut shortest = input.len();
+
+    for l in 0x41..0x5B as u8 {
+        for c in input.chars() {
+            let b = c as u8;
+            if b == l || b == l + 0x20 {
+                continue;
+            }
+
+            match stack.pop() {
+                Some(v) => {
+                    if v != b + 0x20 && v != b - 0x20 {
+                        stack.push(v);
+                        stack.push(b);
+                    }
+                }
+                None => stack.push(b),
+            };
+        }
+
+        if stack.len() < shortest {
+            shortest = stack.len();
+        }
+        stack.clear();
+    }
+
+    shortest as i32
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::collections::HashMap;
+
+    #[test]
+    fn c_05_1_examples() -> Result<(), String> {
+        let mut examples: HashMap<&[&str], &str> = HashMap::new();
+        examples.insert(&["dabAcCaCBAcCcaDA"][..], "10");
+
+        for (input, out) in examples.iter() {
+            let actual = run(input, 1);
+            if &actual != out {
+                return Err(format!("Got: {}, Want: {}", actual, out));
+            }
+        }
+
+        Ok(())
+    }
+
+    #[test]
+    fn c_05_2_examples() -> Result<(), String> {
+        let mut examples: HashMap<&[&str], &str> = HashMap::new();
+        examples.insert(&["dabAcCaCBAcCcaDA"][..], "4");
+
+        for (input, out) in examples.iter() {
+            let actual = run(input, 2);
+            if &actual != out {
+                return Err(format!("Got: {}, Want: {}", actual, out));
+            }
+        }
+
+        Ok(())
+    }
+}

src/aoc/lib.rs

@@ -4,6 +4,7 @@ mod c01;
 mod c02;
 mod c03;
 mod c04;
+mod c05;
 
 pub fn run(input: &[&str], challenge: u8, part: u8) -> String {
     match challenge {
@@ -11,6 +12,7 @@ pub fn run(input: &[&str], challenge: u8, part: u8) -> String {
         2 => c02::run(input, part),
         3 => c03::run(input, part),
         4 => c04::run(input, part),
+        5 => c05::run(input, part),
         _ => panic!("challenge not implemented"),
     }
 }