thallada/advent-of-code-2020
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Use HashMap Entry api in day 15

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Slightly faster and a bit cleaner.
This commit is contained in:
Tyler Hallada 2020-12-15 10:52:36 -05:00
parent 52fafa5716
commit d311aec2e1
1 changed files with 10 additions and 6 deletions
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16
day15/src/main.rs
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@ -1,4 +1,5 @@
use anyhow::{anyhow, Result};
use std::collections::hash_map::Entry;
use std::collections::HashMap;
use std::fs::File;
use std::io::prelude::*;
@ -42,13 +43,16 @@ impl Game {
fn take_turn(&mut self) {
self.turn += 1;
let new_num = if let Some(prev_turn) = self.prev_nums.get(&self.last_num) {
self.turn - prev_turn - 1
} else {
0
self.last_num = match self.prev_nums.entry(self.last_num) {
Entry::Occupied(mut entry) => {
let prev_turn = entry.insert(self.turn - 1);
self.turn - prev_turn - 1
}
Entry::Vacant(entry) => {
entry.insert(self.turn - 1);
0
}
};
self.prev_nums.insert(self.last_num, self.turn - 1);
self.last_num = new_num;
}
}