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Use multiplication and shift for mod

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Bert Peters
2022-12-11 22:03:47 +01:00
parent 6a51f123ab
commit 92db6e56c9
2 changed files with 23 additions and 17 deletions
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1
2022/Cargo.toml
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@@ -11,6 +11,7 @@ anyhow = "1.0.66"
clap = { version = "4.0.19", features = ["derive"] } clap = { version = "4.0.19", features = ["derive"] }
itertools = "0.10.5" itertools = "0.10.5"
nom = "7.1.1" nom = "7.1.1"
strength_reduce = "0.2.4"
[dev-dependencies] [dev-dependencies]
criterion = "0.4.0" criterion = "0.4.0"

39
2022/src/day11.rs
View File

@@ -13,6 +13,7 @@ use nom::sequence::preceded;
use nom::sequence::separated_pair; use nom::sequence::separated_pair;
use nom::sequence::tuple; use nom::sequence::tuple;
use nom::IResult; use nom::IResult;
use strength_reduce::StrengthReducedU64;
use crate::common::parse_input; use crate::common::parse_input;
@@ -37,7 +38,7 @@ impl Operation {
struct Monkey { struct Monkey {
items: Vec<u64>, items: Vec<u64>,
operation: Operation, operation: Operation,
test_mod: u64, test_mod: StrengthReducedU64,
targets: [usize; 2], targets: [usize; 2],
inspected: usize, inspected: usize,
} }
@@ -55,13 +56,13 @@ impl Monkey {
} }
} }
fn handle_items2(&mut self, drains: &mut [Vec<u64>], mod_base: u64) { fn handle_items2(&mut self, drains: &mut [Vec<u64>], mod_base: StrengthReducedU64) {
self.inspected += self.items.len(); self.inspected += self.items.len();
for item in self.items.drain(..) { for item in self.items.drain(..) {
let mut new_val = self.operation.transform(item); let mut new_val = self.operation.transform(item);
// Modular arithmetic is a good way to get less worried // Modular arithmetic is a good way to get less worried
new_val %= mod_base; new_val = new_val % mod_base;
drains[(new_val % self.test_mod == 0) as usize].push(new_val); drains[(new_val % self.test_mod == 0) as usize].push(new_val);
} }
@@ -112,15 +113,27 @@ fn parse_monkey(input: &[u8]) -> IResult<&[u8], Monkey> {
|(items, operation, test_mod, if_true, if_false)| Monkey { |(items, operation, test_mod, if_true, if_false)| Monkey {
items, items,
operation, operation,
test_mod, test_mod: StrengthReducedU64::new(test_mod),
targets: [if_false as usize, if_true as usize], targets: [if_false as usize, if_true as usize],
inspected: 0, inspected: 0,
}, },
)(input) )(input)
} }
fn parse_monkeys(input: &[u8]) -> IResult<&[u8], Vec<Monkey>> {
separated_list0(newline, parse_monkey)(input)
}
fn format_result(mut monkeys: Vec<Monkey>) -> Result<String> {
monkeys.sort_by(|a, b| b.inspected.cmp(&a.inspected));
let result: usize = monkeys[0].inspected * monkeys[1].inspected;
Ok(result.to_string())
}
pub fn part1(input: &[u8]) -> Result<String> { pub fn part1(input: &[u8]) -> Result<String> {
let mut monkeys = parse_input(input, separated_list0(newline, parse_monkey))?; let mut monkeys = parse_input(input, parse_monkeys)?;
let mut drains = [Vec::new(), Vec::new()]; let mut drains = [Vec::new(), Vec::new()];
for _ in 0..20 { for _ in 0..20 {
@@ -134,18 +147,14 @@ pub fn part1(input: &[u8]) -> Result<String> {
} }
} }
monkeys.sort_by(|a, b| b.inspected.cmp(&a.inspected)); format_result(monkeys)
let result: usize = monkeys[0].inspected * monkeys[1].inspected;
Ok(result.to_string())
} }
pub fn part2(input: &[u8]) -> Result<String> { pub fn part2(input: &[u8]) -> Result<String> {
let mut monkeys = parse_input(input, separated_list0(newline, parse_monkey))?; let mut monkeys = parse_input(input, parse_monkeys)?;
let mut drains = [Vec::new(), Vec::new()]; let mut drains = [Vec::new(), Vec::new()];
let mod_base: u64 = monkeys.iter().map(|m| m.test_mod).product(); let mod_base = StrengthReducedU64::new(monkeys.iter().map(|m| m.test_mod.get()).product());
for _ in 0..10000 { for _ in 0..10000 {
for i in 0..monkeys.len() { for i in 0..monkeys.len() {
@@ -158,11 +167,7 @@ pub fn part2(input: &[u8]) -> Result<String> {
} }
} }
monkeys.sort_by(|a, b| b.inspected.cmp(&a.inspected)); format_result(monkeys)
let result: usize = monkeys[0].inspected * monkeys[1].inspected;
Ok(result.to_string())
} }
#[cfg(test)] #[cfg(test)]