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Advent of Code solutions
1use advent_core::{day_stuff, ex_for_day, Day};
2
3pub struct Day7;
4
5impl Day for Day7 {
6 day_stuff!(7, "3749", "11387", Vec<(i64, Vec<i64>)>);
7
8 fn part_1(input: Self::Input) -> Option<String> {
9 let ans = input
10 .into_iter()
11 .filter_map(|(target, operands)| {
12 let ps: u64 = 1 << (operands.len() - 1);
13 for p in 0..=ps {
14 let res = operands.iter().enumerate().fold(0, |acc, (i, e)| {
15 if i == 0 {
16 acc + *e
17 } else if p & (1 << (i - 1)) != 0 {
18 acc * *e
19 } else {
20 acc + *e
21 }
22 });
23 if res == target {
24 return Some(target);
25 }
26 }
27 None
28 })
29 .sum::<i64>();
30
31 Some(ans.to_string())
32 }
33
34 fn part_2(input: Self::Input) -> Option<String> {
35 let ans = input
36 .into_iter()
37 .filter_map(|(target, operands)| {
38 let ps: u64 = 3_u64.pow((operands.len() - 1) as u32);
39 for p in 0..=ps {
40 let res = operands.iter().enumerate().fold(0, |acc, (i, e)| {
41 if i == 0 {
42 acc + *e
43 } else if p / 3_u64.pow((i - 1) as u32) % 3 == 1 {
44 acc * *e
45 } else if p / 3_u64.pow((i - 1) as u32) % 3 == 2 {
46 // Integer logartihm to prevent calls to to_string?
47 format!("{acc}{e}").parse().unwrap()
48 } else {
49 acc + *e
50 }
51 });
52 if res == target {
53 return Some(target);
54 }
55 }
56 None
57 })
58 .sum::<i64>();
59
60 Some(ans.to_string())
61 }
62
63 fn parse_input(input: &str) -> Self::Input {
64 input
65 .lines()
66 .map(|l| {
67 let (eq, rest) = l.split_once(": ").unwrap();
68 (
69 eq.parse().unwrap(),
70 rest.split(" ").map(|x| x.parse().unwrap()).collect(),
71 )
72 })
73 .collect()
74 }
75}