Day 6 optimized + Day 7

src/day06.rs

@@ -1,32 +1,33 @@
 use aoc_runner_derive::{aoc, aoc_generator};
 
-type Data = Vec<u8>;
+type Data = [usize;9];
 
 #[aoc_generator(day06)]
-pub fn input_generator(input: &str) -> Data {
-    input.trim().split(',').map(|v| v.parse().unwrap()).collect()
+pub fn input_generator(input: &str) -> [usize;9] {
+    let mut state: [usize;9] = [0;9];
+    let input = input.trim().split(',').map(|v| v.parse::<usize>().unwrap());
+    for v in input {
+        state[v]+=1;
+    }
+    state
 }
 
 
 fn simulate(input: &Data,n: usize) -> usize {
-    let mut state: [usize;9] = [0;9];
-    for v in input {
-        state[*v as usize]+=1;
-    }
-    for _ in 0..n {
-        state[7]+=state[0];
-        state.rotate_left(1);
+    let mut state=*input;
+    for i in 0..n {
+        state[(7+i)%9]+=state[i%9];
     }
     state.iter().sum()
 
 }
 
-#[aoc(day06, part1)]
+#[aoc(day06, part1)] // 353274
 pub fn solve_part1(input: &Data) -> usize {
     simulate(input,80)
 }
 
-#[aoc(day06, part2)]
+#[aoc(day06, part2)] // 1609314870967
 pub fn solve_part2(input: &Data) -> usize {
     simulate(input,256)
 }

src/day07.rs

@@ -0,0 +1,33 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+type Data = Vec<i64>;
+
+#[aoc_generator(day07)]
+pub fn input_generator(input: &str) -> Data {
+    let mut input: Vec<_> = input.split(',').map(|v| v.parse().unwrap()).collect();
+    input.sort_unstable();
+    input
+}
+
+#[aoc(day07, part1)] // 336040
+pub fn solve_part1(input: &Data) -> i64 {
+    let start = *input.first().unwrap();
+    let end = *input.last().unwrap();
+    (start..=end).map(|n| {
+        input.iter().map(|v| {
+            (v-n).abs()
+        }).sum()
+    }).min().unwrap()
+}
+
+#[aoc(day07, part2)] // 94813675
+pub fn solve_part2(input: &Data) -> i64 {
+    let start = *input.first().unwrap();
+    let end = *input.last().unwrap();
+    (start..=end).map(|n| {
+        input.iter().map(|v| {
+            let diff=(v-n).abs();
+            (diff*(diff+1))>>1 // Gauss
+        }).sum()
+    }).min().unwrap()
+}

src/lib.rs

@@ -1,4 +1,6 @@
 #![allow(clippy::clippy::needless_return)]
+#![feature(int_abs_diff)]
+
 use aoc_runner_derive::aoc_lib;
 pub mod day01;
 pub mod day02;
@@ -6,4 +8,5 @@ pub mod day03;
 pub mod day04;
 pub mod day05;
 pub mod day06;
+pub mod day07;
 aoc_lib! { year = 2021 }

src/main.rs

@@ -1,2 +1,3 @@
+#![feature(int_abs_diff)]
 use aoc_runner_derive::aoc_main;
 aoc_main! { lib  = aoc_2021 }