21: avoid allocations to string

AxlLind · Dec 21, 2022 · e25fe4d · e25fe4d
1 parent 74411c4
commit e25fe4d
Showing 1 changed file with 20 additions and 19 deletions.
diff --git a/src/bin/21.rs b/src/bin/21.rs
@@ -1,15 +1,15 @@
 use hashbrown::HashMap;
 use itertools::Itertools;
 
-enum Op {
+enum Op<'a> {
   Num(i64),
-  Add(String, String),
-  Sub(String, String),
-  Mul(String, String),
-  Div(String, String),
+  Add(&'a str, &'a str),
+  Sub(&'a str, &'a str),
+  Mul(&'a str, &'a str),
+  Div(&'a str, &'a str),
 }
 
-fn val(monkies: &HashMap<String, Op>, cache: &mut HashMap<String, i64>, name: &str) -> i64 {
+fn val<'a>(monkies: &'a HashMap<&str, Op>, cache: &mut HashMap<&'a str, i64>, name: &'a str) -> i64 {
   if let Some(&v) = cache.get(name) {
     return v;
   }
@@ -20,11 +20,14 @@ fn val(monkies: &HashMap<String, Op>, cache: &mut HashMap<String, i64>, name: &s
     Op::Mul(m1, m2) => val(monkies, cache, &m1) * val(monkies, cache, &m2),
     Op::Div(m1, m2) => val(monkies, cache, &m1) / val(monkies, cache, &m2),
   };
-  cache.insert(name.to_string(), v);
+  cache.insert(name, v);
   v
 }
 
-fn get_eq(monkies: &HashMap<String, Op>, name: &str) -> String {
+fn get_eq(monkies: &HashMap<&str, Op>, name: &str) -> String {
+  if name == "humn" {
+    return "x".to_string();
+  }
   match &monkies[name] {
     Op::Num(i) => i.to_string(),
     Op::Add(m1, m2) => format!("({} + {})", get_eq(monkies, &m1), get_eq(monkies, &m2)),
@@ -36,20 +39,18 @@ fn get_eq(monkies: &HashMap<String, Op>, name: &str) -> String {
 
 #[aoc::main(21)]
 fn main(input: &str) -> (i64, &str) {
-  let mut monkies = input.lines().map(|l| {
+  let monkies = input.lines().map(|l| {
     let (name, rest) = l.split_once(": ").unwrap();
     let op = match rest.split(' ').collect_tuple() {
-      Some((m1, "+", m2)) => Op::Add(m1.to_string(), m2.to_string()),
-      Some((m1, "-", m2)) => Op::Sub(m1.to_string(), m2.to_string()),
-      Some((m1, "*", m2)) => Op::Mul(m1.to_string(), m2.to_string()),
-      Some((m1, "/", m2)) => Op::Div(m1.to_string(), m2.to_string()),
+      Some((m1, "+", m2)) => Op::Add(m1, m2),
+      Some((m1, "-", m2)) => Op::Sub(m1, m2),
+      Some((m1, "*", m2)) => Op::Mul(m1, m2),
+      Some((m1, "/", m2)) => Op::Div(m1, m2),
       _ => Op::Num(rest.parse().unwrap()),
     };
-    (name.to_string(), op)
-  }).collect::<HashMap<_,_>>();
+    (name, op)
+  }).collect();
   let mut values = HashMap::new();
-  let p1 = val(&monkies, &mut values, "root");
-  monkies.insert("humn".to_string(), Op::Num(-1337));
-  println!("{} = {}", val(&monkies, &mut values, "tfjf"), get_eq(&monkies, "vtsj").replace("-1337", "x"));
-  (p1,"glhf -> https://www.mathpapa.com/equation-solver/")
+  println!("{} = {}", val(&monkies, &mut values, "tfjf"), get_eq(&monkies, "vtsj"));
+  (val(&monkies, &mut values, "root"), "glhf -> https://www.mathpapa.com/equation-solver/")
 }