Add day 21

Cargo.toml

@@ -88,4 +88,9 @@ path = "src/day19/main.rs"
 [[bin]]
 name = "day20"
 path = "src/day20/main.rs"
+
+[[bin]]
+name = "day21"
+path = "src/day21/main.rs"
+
 [dependencies]

day21_test.txt

@@ -0,0 +1,15 @@
+root: pppw + sjmn
+dbpl: 5
+cczh: sllz + lgvd
+zczc: 2
+ptdq: humn - dvpt
+dvpt: 3
+lfqf: 4
+humn: 5
+ljgn: 2
+sjmn: drzm * dbpl
+sllz: 4
+pppw: cczh / lfqf
+lgvd: ljgn * ptdq
+drzm: hmdt - zczc
+hmdt: 32

src/day21/main.rs

@@ -0,0 +1,90 @@
+use std::collections::HashMap;
+use base::read_file;
+
+#[derive(Clone, Debug)]
+enum UnparsedOp {
+    Constant(i64),
+    Add(String, String),
+    Sub(String, String),
+    Mul(String, String),
+    Div(String, String),
+}
+
+fn solve_op(op: &UnparsedOp, data: &HashMap<String, UnparsedOp>) -> i64 {
+    return match op {
+        UnparsedOp::Constant(number) => *number,
+        UnparsedOp::Add(f, s) => solve_op(&data[f], data) + solve_op(&data[s], data),
+        UnparsedOp::Sub(f, s) => solve_op(&data[f], data) - solve_op(&data[s], data),
+        UnparsedOp::Mul(f, s) => solve_op(&data[f], data) * solve_op(&data[s], data),
+        UnparsedOp::Div(f, s) => solve_op(&data[f], data) / solve_op(&data[s], data),
+    };
+}
+
+fn solve(data: &HashMap<String, UnparsedOp>) -> i64 {
+    let root = &data["root"];
+
+    solve_op(root, data)
+}
+
+fn solve_eq(data: &mut HashMap<String, UnparsedOp>) -> i64 {
+    let root = data["root"].clone();
+
+
+    if let UnparsedOp::Add(f, s) = root {
+        let mut guess = 0;
+        let mut add = 100000000000;
+
+        loop {
+            let new_guess = guess + add;
+            data.insert("humn".to_owned(), UnparsedOp::Constant(new_guess));
+            let left = solve_op(&data[&f], data);
+            let right = solve_op(&data[&s], data);
+            if left < right {
+                add /= 10;
+            } else {
+                guess = new_guess;
+            }
+
+            if left == right {
+                return guess;
+            }
+        }
+
+    } else {
+        panic!("Can't handle this");
+    }
+}
+
+fn main() {
+    let lines = read_file("day21.txt");
+    let mut data = HashMap::new();
+
+    for line in lines {
+        let splits = line.split(": ").collect::<Vec<_>>();
+        let name = splits[0];
+        if let Ok(number) = splits[1].parse::<i64>() {
+            data.insert(name.to_owned(), UnparsedOp::Constant(number));
+        } else {
+            let split_op = splits[1].split_whitespace().collect::<Vec<_>>();
+            let first = split_op[0].to_owned();
+            let second = split_op[2].to_owned();
+
+            data.insert(name.to_owned(), match split_op[1].chars().next().unwrap() {
+                '+' => UnparsedOp::Add(first, second),
+                '-' => UnparsedOp::Sub(first, second),
+                '*' => UnparsedOp::Mul(first, second),
+                '/' => UnparsedOp::Div(first, second),
+                _ => {
+                    panic!("Unknown operation");
+                }
+            });
+        }
+    }
+
+    let result = solve(&data);
+    println!("Task1: {}", result);
+
+
+    let result = solve_eq(&mut data);
+    println!("Task2: {}", result);
+}