Some solutions to AOC 2020

1 files changed, 47 insertions, 0 deletions

diff --git a/2020/Rust/src/day1.rs b/2020/Rust/src/day1.rs
new file mode 100755
index 0000000..9a84dd4
--- /dev/null
+++ b/2020/Rust/src/day1.rs
@@ -0,0 +1,47 @@
+use std::collections::HashSet;
+
+fn solve_part_one(input: &str) -> i32 {
+    let mut seen = HashSet::new();
+    let numbers: Vec<i32> = input
+        .lines()
+        .map(|line| line.trim().parse().unwrap())
+        .collect();
+
+    for &number in &numbers {
+        let complement = 2020 - number;
+        if seen.contains(&complement) {
+            return number * complement;
+        }
+        seen.insert(number);
+    }
+    panic!("No two numbers sum to 2020!");
+}
+
+fn solve_part_two(input: &str) -> i32 {
+    let numbers: Vec<i32> = input
+        .lines()
+        .map(|line| line.trim().parse().unwrap())
+        .collect();
+
+    for (i, &first) in numbers.iter().enumerate() {
+        let mut seen = HashSet::new();
+        let target_sum = 2020 - first;
+        for &second in &numbers[i + 1..] {
+            let complement = target_sum - second;
+            if seen.contains(&complement) {
+                return first * second * complement;
+            }
+            seen.insert(second);
+        }
+    }
+    panic!("No three numbers sum to 2020!");
+}
+
+fn main() {
+    let test = include_str!("../input/day_1.test");
+    let prod = include_str!("../input/day_1.prod");
+    println!("Test_1: {}", solve_part_one(test));
+    println!("Prod_1: {}", solve_part_one(prod));
+    println!("Test_2: {}", solve_part_two(test));
+    println!("Prod_2: {}", solve_part_two(prod));
+}