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2020: day01: quadratic part 2

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This commit is contained in:
Antoine Martin 2020-12-01 17:15:33 +01:00
parent a948437488
commit 14756db40a
1 changed files with 21 additions and 19 deletions
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30
aoc2020/src/day01.rs
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@ -1,3 +1,4 @@
use std::collections::HashSet;
use std::fmt::Write;
use aoc::{err, Result};
@ -13,29 +14,29 @@ pub fn run() -> Result<String> {
Ok(res)
}
fn part1(input: &str) -> Result<u64> {
fn part1(input: &str) -> Result<i64> {
let entries = input
.lines()
.map(|line| line.parse::<u64>().map_err(|e| err!("{}", e)))
.collect::<Result<Vec<u64>>>()?;
.map(|line| line.parse::<i64>().map_err(|e| err!("{}", e)))
.collect::<Result<Vec<i64>>>()?;
let (a, b) = find_2020_2_sum(&entries)?;
Ok(a * b)
}
fn part2(input: &str) -> Result<u64> {
fn part2(input: &str) -> Result<i64> {
let entries = input
.lines()
.map(|line| line.parse::<u64>().map_err(|e| err!("{}", e)))
.collect::<Result<Vec<u64>>>()?;
.map(|line| line.parse::<i64>().map_err(|e| err!("{}", e)))
.collect::<Result<Vec<i64>>>()?;
let (a, b, c) = find_2020_3_sum(&entries)?;
Ok(a * b * c)
}
fn find_2020_2_sum(entries: &[u64]) -> Result<(u64, u64)> {
fn find_2020_2_sum(entries: &[i64]) -> Result<(i64, i64)> {
for i in 0..entries.len() {
for j in 0..entries.len() {
if i == j {
@ -50,24 +51,25 @@ fn find_2020_2_sum(entries: &[u64]) -> Result<(u64, u64)> {
Err(err!("couldn't find 2 elements that sum to 2020"))
}
fn find_2020_3_sum(entries: &[u64]) -> Result<(u64, u64, u64)> {
fn find_2020_3_sum(entries: &[i64]) -> Result<(i64, i64, i64)> {
let set: HashSet<i64> = entries.iter().copied().collect();
for i in 0..entries.len() {
for j in 0..entries.len() {
for k in 0..entries.len() {
if i == j || j == k || k == i {
if i == j {
continue;
}
let a = entries[i];
let b = entries[j];
let c = entries[k];
if a + b + c == 2020 {
let c = 2020 - a - b;
if set.contains(&c) {
return Ok((a, b, c));
}
}
}
}
Err(err!("couldn't find 2 elements that sum to 2020"))
}
@ -76,7 +78,7 @@ fn find_2020_3_sum(entries: &[u64]) -> Result<(u64, u64, u64)> {
mod tests {
use super::*;
static PROVIDED: &[u64] = &[1721, 979, 366, 299, 675, 1456];
static PROVIDED: &[i64] = &[1721, 979, 366, 299, 675, 1456];
#[test]
fn part1_provided() {