Day 7

src/day7.rs

@@ -0,0 +1,67 @@
+use itertools::{repeat_n, Itertools};
+use rayon::prelude::*;
+use regex::Regex;
+
+pub fn day7() {
+    let lines: Vec<(u64, Vec<u64>)> = parse_input(&crate::input(7));
+
+    let simple_operations = vec![Operation::Add, Operation::Mul];
+    let simple_operations_total: u64 = lines
+        .par_iter()
+        .filter(|(goal, operands)| possible_totals(operands, &simple_operations).contains(goal))
+        .map(|(goal, _)| goal)
+        .sum();
+
+    let all_operations = vec![Operation::Add, Operation::Mul, Operation::Cat];
+    let all_operations_total: u64 = lines
+        .par_iter()
+        .filter(|(goal, operands)| possible_totals(operands, &all_operations).contains(goal))
+        .map(|(goal, _)| goal)
+        .sum();
+
+    println!("Total for +/*: {}", simple_operations_total);
+    println!("Total for All: {}", all_operations_total);
+}
+
+fn possible_totals(operands: &Vec<u64>, operations: &Vec<Operation>) -> Vec<u64> {
+    repeat_n(operations, operands.len() - 1)
+        .multi_cartesian_product()
+        .map(|operations| {
+            operands[1..]
+                .iter()
+                .zip(operations)
+                .fold(operands[0], |acc, (e, op)| op.apply(acc, *e))
+        })
+        .collect()
+}
+
+fn parse_input(input: &str) -> Vec<(u64, Vec<u64>)> {
+    input
+        .lines()
+        .map(|line| {
+            let all: Vec<u64> = Regex::new(r"\D+")
+                .unwrap()
+                .split(line)
+                .map(|s| s.parse().unwrap())
+                .collect();
+            (all[0], all[1..].to_vec())
+        })
+        .collect()
+}
+
+#[derive(Clone)]
+enum Operation {
+    Add,
+    Mul,
+    Cat,
+}
+
+impl Operation {
+    fn apply(&self, a: u64, b: u64) -> u64 {
+        match self {
+            Self::Add => a + b,
+            Self::Mul => a * b,
+            Self::Cat => (a.to_string() + &b.to_string()).parse().unwrap(),
+        }
+    }
+}

src/main.rs

@@ -1,12 +1,19 @@
+#[allow(dead_code)]
 mod day1;
+#[allow(dead_code)]
 mod day2;
+#[allow(dead_code)]
 mod day3;
+#[allow(dead_code)]
 mod day4;
+#[allow(dead_code)]
 mod day5;
+#[allow(dead_code)]
 mod day6;
+mod day7;
 
 fn main() {
-    day6::day6();
+    day7::day7();
 }
 
 pub fn input(day: u8) -> String {