solution: day20

Cargo.lock

@@ -394,9 +394,9 @@ dependencies = [
 
 [[package]]
 name = "ipnet"
-version = "2.5.1"
+version = "2.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f88c5561171189e69df9d98bcf18fd5f9558300f7ea7b801eb8a0fd748bd8745"
+checksum = "11b0d96e660696543b251e58030cf9787df56da39dab19ad60eae7353040917e"
 
 [[package]]
 name = "itertools"
@@ -716,9 +716,9 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.149"
+version = "1.0.150"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "256b9932320c590e707b94576e3cc1f7c9024d0ee6612dfbcf1cb106cbe8e055"
+checksum = "e326c9ec8042f1b5da33252c8a37e9ffbd2c9bef0155215b6e6c80c790e05f91"
 
 [[package]]
 name = "serde_json"

src/bin/20.rs

@@ -0,0 +1,43 @@
+pub fn part_one(input: &str) -> Option<u32> {
+    let limit = input.parse::<usize>().unwrap() / 10;
+    let elves = 1_000_000;
+    let mut delivered = vec![0; elves];
+    for i in 1..elves {
+        for j in (i..elves).step_by(i) {
+            delivered[j] += i;
+        }
+    }
+
+    Some(
+        delivered
+            .iter()
+            .enumerate()
+            .find(|(_, &x)| x > limit)
+            .unwrap()
+            .0 as u32,
+    )
+}
+pub fn part_two(input: &str) -> Option<u32> {
+    let limit = input.parse().unwrap();
+    let elves = 1_000_000;
+    let mut delivered = vec![0; elves];
+    for i in 1..elves {
+        for j in (i..elves).step_by(i).take(50) {
+            delivered[j] += i * 11;
+        }
+    }
+
+    Some(
+        delivered
+            .iter()
+            .enumerate()
+            .find(|(_, &x)| x > limit)
+            .unwrap()
+            .0 as u32,
+    )
+}
+fn main() {
+    let input = &aoc::read_file("inputs", 20);
+    aoc::solve!(1, part_one, input);
+    aoc::solve!(2, part_two, input);
+}