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day6: optimized with quadratic inequality

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This commit is contained in:
Ishan Jain 2023-12-06 13:13:11 +05:30
parent 9787958cc4
commit 0171ee6758
Signed by: ishan
GPG Key ID: 0506DB2A1CC75C27
2 changed files with 66 additions and 45 deletions
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57
src/day6/1.rs
View File

@ -2,48 +2,65 @@
extern crate test; extern crate test;
const INPUTS: [&str; 2] = [include_str!("./sample.txt"), include_str!("./input.txt")]; const INPUTS: [&[u8]; 2] = [
include_bytes!("./sample.txt"),
include_bytes!("./input.txt"),
];
fn process(data: &str) -> i64 { fn process(data: &[u8]) -> u64 {
let mut data = data.lines(); let mut data = data.split(|&x| x == b'\n');
let time = data let time = data
.next() .next()
.map(|line| { .map(|line| {
line.split(' ') line.split(|&x| x == b' ')
.filter(|x| !x.is_empty())
.skip(1) .skip(1)
.map(|x| x.parse::<u64>().unwrap()) .filter(|c| !c.is_empty())
.map(|c| {
let mut num = 0;
let mut mul = 1;
for c in c.iter().rev() {
num += (c - b'0') as u64 * mul;
mul *= 10;
}
num as f32
})
}) })
.unwrap(); .unwrap();
let distance = data let distance = data
.next() .next()
.map(|line| { .map(|line| {
line.split(' ') line.split(|&x| x == b' ')
.filter(|x| !x.is_empty())
.skip(1) .skip(1)
.map(|x| x.parse::<u64>().unwrap()) .filter(|c| !c.is_empty())
.map(|c| {
let mut num = 0;
let mut mul = 1;
for c in c.iter().rev() {
num += (c - b'0') as u64 * mul;
mul *= 10;
}
num as f32
})
}) })
.unwrap(); .unwrap();
let mut answer = 1; let mut answer = 1;
for (time, dist) in time.zip(distance) { for (time, dist) in time.zip(distance) {
let mut ways = 0; let mut root1 = (time + (time * time - 4.0 * dist).sqrt()) / 2.0;
let root2 = (time - (time * time - 4.0 * dist).sqrt()) / 2.0;
for t in 0..time { if root1.fract() == 0.0 && root2.fract() == 0.0 {
let time_left = time - t; root1 -= 1.0;
let speed = t;
let dist_traveled = time_left * speed;
if dist_traveled > dist {
ways += 1;
}
} }
answer *= ways; answer *= root1 as u64 - root2 as u64;
} }
answer answer

54
src/day6/2.rs
View File

@ -2,42 +2,46 @@
extern crate test; extern crate test;
const INPUTS: [&str; 2] = [include_str!("./sample.txt"), include_str!("./input.txt")]; const INPUTS: [&[u8]; 2] = [
include_bytes!("./sample.txt"),
include_bytes!("./input.txt"),
];
fn process(data: &str) -> i64 { fn process(data: &[u8]) -> u64 {
let mut data = data.lines(); let mut data = data.split(|&x| x == b'\n');
let time: u64 = data let time: f64 = data
.next() .next()
.map(|line| { .map(|line| {
let x: String = line.chars().filter(|c| c.is_numeric()).collect(); let mut num = 0;
let mut mul = 1;
x.parse::<u64>().unwrap() for c in line.iter().filter(|c| c.is_ascii_digit()).rev() {
num += (c - b'0') as u64 * mul;
mul *= 10;
}
num as f64
}) })
.unwrap_or(0); .unwrap_or(0.0);
let distance: u64 = data let distance: f64 = data
.next() .next()
.map(|line| { .map(|line| {
let x: String = line.chars().filter(|c| c.is_numeric()).collect(); let mut num = 0;
let mut mul = 1;
x.parse::<u64>().unwrap() for c in line.iter().filter(|c| c.is_ascii_digit()).rev() {
num += (c - b'0') as u64 * mul;
mul *= 10;
}
num as f64
}) })
.unwrap_or(0); .unwrap_or(0.0);
let mut answer = 0; let mut root1 = (time + (time.powi(2) - 4.0 * distance).sqrt()) / 2.0;
let root2 = (time - (time.powi(2) - 4.0 * distance).sqrt()) / 2.0;
for t in 0..time { if root1.fract() == 0.0 && root2.fract() == 0.0 {
let time_left = time - t; root1 -= 1.0;
let speed = t;
let dist_traveled = time_left * speed;
if dist_traveled > distance {
answer += 1;
}
} }
answer root1 as u64 - root2 as u64
} }
fn main() { fn main() {