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main.rs
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#![feature(test)]
extern crate test;
use anyhow::Result;
use common::Answer;
use std::{collections::VecDeque, io};
pub fn main() -> Result<()> {
let stdin = io::read_to_string(io::stdin())?;
println!("part1: {}", part_one(&stdin)?);
println!("part2: {}", part_two(&stdin)?);
Ok(())
}
pub fn part_one(input: &str) -> Result<Answer> {
let input = parse_input(input)?;
solve_one(&input)
}
pub fn part_two(input: &str) -> Result<Answer> {
let input = parse_input(input)?;
solve_two(&input)
}
struct Input {
blocks: VecDeque<Block>,
gaps: VecDeque<Block>,
}
#[derive(Debug, Clone, Copy)]
struct Block {
start: usize,
len: usize,
id: i128,
}
impl Block {
fn print(&self) {
// print!("s{}:", self.start);
for _i in 0..self.len {
print!("{}", self.id);
}
// print!(" ");
}
fn checksum(&self) -> i128 {
let mut sum = 0;
for u in self.start..self.start + self.len {
sum += u as i128 * self.id;
}
sum
}
}
fn parse_input(input: &str) -> Result<Input> {
let nums: Vec<u32> = input.chars().filter_map(|c| c.to_digit(10)).collect();
let mut blocks = VecDeque::new();
let mut gaps = VecDeque::new();
let mut gap = false;
let mut start = 0;
let mut id = 0;
for n in nums {
let block = Block {
start,
len: n as usize,
id,
};
if n != 0 {
if gap {
gaps.push_back(block);
} else {
blocks.push_back(block);
}
}
gap = !gap;
start = start + n as usize;
if !gap {
id += 1;
}
}
Ok(Input { blocks, gaps })
}
fn solve_one(input: &Input) -> Result<Answer> {
let Input { blocks, gaps } = input;
let mut blocks = blocks.clone();
let mut gaps = gaps.clone();
// 2 3g 3 3g 1 3g 3 1g 2 1g 4 1g 4 1g 3 1g 4 0g 2
// 2 3 1 3 2 4 4 3 4 2
// 3 3 3 1 1 1 1 1
//
// 2 2 1g 3 3g 1 3g 3 1g 2 1g 4 1g 4 1g 3 1g 4
// 2 2 1 3 3g 1 3g 3 1g 2 1g 4 1g 4 1g 3 1g 3
// 2 2 1 3 3 1 3g 3 1g 2 1g 4 1g 4 1g 3 1g
// 2 2 1 3 3 1 3g 3 1g 2 1g 4 1g 4 1g 3
// 2 2 1 3 3 1 3g 3 1g 2 1g 4 1g 4 1g 3
let mut result_blocks: Vec<Block> = Vec::new();
while let Some(gap_to_fill) = gaps.pop_front() {
if let Some(block_to_move) = blocks.pop_back() {
// println!("moving {:?} to gap {:?}", block_to_move, gap_to_fill);
if block_to_move.start < gap_to_fill.start {
blocks.push_back(block_to_move); // block was already better placed!
break;
}
if gap_to_fill.len > block_to_move.len {
result_blocks.push(Block {
start: gap_to_fill.start,
len: block_to_move.len,
id: block_to_move.id,
});
gaps.push_front(Block {
start: gap_to_fill.start + block_to_move.len,
len: gap_to_fill.len - block_to_move.len,
id: gap_to_fill.id,
});
} else if gap_to_fill.len < block_to_move.len {
result_blocks.push(Block {
start: gap_to_fill.start,
len: gap_to_fill.len,
id: block_to_move.id,
});
blocks.push_back(Block {
start: block_to_move.start,
len: block_to_move.len - gap_to_fill.len,
id: block_to_move.id,
});
} else {
result_blocks.push(Block {
start: gap_to_fill.start,
len: gap_to_fill.len,
id: block_to_move.id,
})
}
}
}
while let Some(block) = blocks.pop_back() {
result_blocks.push(block);
}
result_blocks.sort_by(|&a, &b| a.start.cmp(&b.start));
// for b in result_blocks {
// b.print()
// }
// println!();
let mut sum = 0;
for b in result_blocks {
sum += b.checksum();
}
Ok(Answer::Num(sum))
}
fn solve_two(input: &Input) -> Result<Answer> {
let Input { blocks, gaps } = input;
let mut blocks = blocks.clone();
let mut gaps = gaps.clone();
let mut result_blocks: Vec<Block> = Vec::new();
while let Some(block) = blocks.pop_back() {
let mut gap_idx = None;
for (idx, gap) in gaps.iter().enumerate() {
if gap.len >= block.len && gap.start < block.start {
result_blocks.push(Block {
start: gap.start,
len: block.len,
id: block.id,
});
gap_idx = Some(idx);
break;
}
}
if let Some(gap_idx) = gap_idx {
let old_gap = gaps[gap_idx].clone();
if old_gap.len == block.len {
gaps.remove(gap_idx);
} else {
gaps[gap_idx] = Block {
start: old_gap.start + block.len,
len: old_gap.len - block.len,
id: old_gap.id,
};
}
// sort order of gaps doesn't matter
gaps.push_back(block);
} else {
result_blocks.push(block);
}
}
result_blocks.sort_by(|&a, &b| a.start.cmp(&b.start));
// for b in result_blocks.iter() {
// b.print()
// }
// println!();
let mut pos = 0;
for b in result_blocks.iter() {
while pos < b.start {
print!(".");
pos += 1;
}
b.print();
pos += b.len;
}
let mut sum = 0;
for b in result_blocks {
sum += b.checksum();
}
//00992111777.44.333....5555.6666.....8888
//00992111777.44.333....5555.6666.....8888..
Ok(Answer::Num(sum))
}
// Quickly obtain answers by running
// cargo test one [-r]
// cargo test two [-r]
#[cfg(test)]
mod day09_tests {
use super::*;
use common::test_utils::*;
use std::sync::LazyLock;
use test::Bencher;
static TEST: LazyLock<String> = local_file!("test");
static INPUT: LazyLock<String> = local_file!("input");
#[test]
fn test_one() -> Result<()> {
let answer = super::part_one(&TEST)?;
assert_eq!(answer, Answer::Num(1928));
Ok(())
}
fn part_one_impl() -> Result<()> {
let answer = super::part_one(&INPUT)?;
assert_eq!(answer, Answer::Num(6370402949053));
Ok(())
}
#[bench]
fn part_one(b: &mut Bencher) {
part_one_impl().expect("Error");
b.iter(|| part_one_impl())
}
#[test]
fn test_two() -> Result<()> {
let answer = super::part_two(&TEST)?;
assert_eq!(answer, Answer::Num(2858));
Ok(())
}
fn part_two_impl() -> Result<()> {
let answer = super::part_two(&INPUT)?;
assert_eq!(answer, Answer::Num(6398096697992));
Ok(())
}
#[bench]
fn part_two(b: &mut Bencher) {
part_two_impl().expect("Error");
b.iter(|| part_two_impl())
}
}