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day7 fast

This commit is contained in:
Jan-Bulthuis 2024-12-07 15:48:34 +01:00
parent 6d557c35cf
commit a7416ed056
1 changed files with 20 additions and 25 deletions
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45
aoc_2024/src/day7.rs
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@ -23,19 +23,19 @@ fn parse(input: &str) -> Input {
fn part1(input: &Input) -> usize { fn part1(input: &Input) -> usize {
input input
.iter() .iter()
.filter(|v| part1_test(v.1[0], v.0, &v.1[1..])) .filter(|v| part1_test(v.1[0] as i64, v.0 as i64, &v.1[1..]))
.fold(0, |acc, v| acc + v.0 as usize) .fold(0, |acc, v| acc + v.0 as usize)
} }
fn part1_test(curr: u64, target: u64, numbers: &[u64]) -> bool { fn part1_test(target: i64, remaining: i64, numbers: &[u64]) -> bool {
if curr > target { if numbers.is_empty() {
false remaining == target
} else if numbers.is_empty() {
curr == target
} else { } else {
let num = numbers[0]; let num = numbers[numbers.len() - 1] as i64;
let rest = &numbers[1..]; let rest = &numbers[0..numbers.len() - 1];
part1_test(curr + num, target, rest) || part1_test(curr * num, target, rest) let mul = remaining % num == 0 && part1_test(target, remaining / num, rest);
let add = part1_test(target, remaining - num, rest);
mul || add
} }
} }
@ -43,26 +43,21 @@ fn part1_test(curr: u64, target: u64, numbers: &[u64]) -> bool {
fn part2(input: &Input) -> usize { fn part2(input: &Input) -> usize {
input input
.iter() .iter()
.filter(|v| part2_test(v.1[0], v.0, &v.1[1..])) .filter(|v| part2_test(v.1[0] as i64, v.0 as i64, &v.1[1..]))
.fold(0, |acc, v| acc + v.0 as usize) .fold(0, |acc, v| acc + v.0 as usize)
} }
fn concat(a: u64, b: u64) -> u64 { fn part2_test(target: i64, remaining: i64, numbers: &[u64]) -> bool {
let digits = b.ilog10() + 1; if numbers.is_empty() {
a * 10u64.pow(digits) + b remaining == target
}
fn part2_test(curr: u64, target: u64, numbers: &[u64]) -> bool {
if curr > target {
false
} else if numbers.is_empty() {
curr == target
} else { } else {
let num = numbers[0]; let num = numbers[numbers.len() - 1] as i64;
let rest = &numbers[1..]; let rest = &numbers[0..numbers.len() - 1];
part2_test(curr + num, target, rest) let mul = remaining % num == 0 && part2_test(target, remaining / num, rest);
|| part2_test(curr * num, target, rest) let pow = 10i64.pow(num.ilog10() + 1);
|| part2_test(concat(curr, num), target, rest) let con = remaining % pow == num && part2_test(target, remaining / pow, rest);
let add = part2_test(target, remaining - num, rest);
mul || con || add
} }
} }