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Add (much slower) sort and binary search day 9 part 1

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This commit is contained in:
Bill Thiede 2020-12-09 18:04:50 -08:00
parent 68d161f2f7
commit 1af8eab8c2
1 changed files with 24 additions and 1 deletions
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25
2020/src/day9.rs
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@ -87,7 +87,6 @@ fn parse(input: &str) -> Vec<usize> {
fn solution1_impl(nums: &[usize], win_size: usize) -> usize {
nums.windows(win_size + 1)
// TODO(wathiede): try soring and/or hashmap for speed.
.skip_while(|chunk| {
let past = &chunk[..win_size];
let cur = chunk[win_size];
@ -104,11 +103,35 @@ fn solution1_impl(nums: &[usize], win_size: usize) -> usize {
.unwrap()
}
fn solution1_impl_sorted(nums: &[usize], win_size: usize) -> usize {
nums.windows(win_size + 1)
.skip_while(|chunk| {
let mut past = (&chunk[..win_size]).clone().to_owned();
past.sort_unstable();
let cur = chunk[win_size];
for p in &past {
let diff = if cur > *p { cur - p } else { p - cur };
if past.binary_search(&diff).is_ok() {
return true;
}
}
false
})
.find_map(|chunk| Some(chunk[win_size]))
.unwrap()
}
#[aoc(day9, part1)]
fn solution1(nums: &[usize]) -> usize {
solution1_impl(nums, 25)
}
#[aoc(day9, part1, sorted)]
fn solution1_sorted(nums: &[usize]) -> usize {
solution1_impl_sorted(nums, 25)
}
fn sum_min_max(low: usize, hi: usize, nums: &[usize]) -> usize {
let (min, max) = nums[low..hi]
.iter()