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Add day 6 part 2 solution

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This commit is contained in:
Wesley Moore 2017-12-09 14:55:33 +10:00
parent 8beb899b36
commit 37bef8869f
1 changed files with 14 additions and 10 deletions
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24
2017/day/6/src/main.rs
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@ -1,7 +1,7 @@
use std::fs::File; use std::fs::File;
use std::io::{Read}; use std::io::{Read};
use std::str::FromStr; use std::str::FromStr;
use std::collections::HashSet; use std::collections::HashMap;
fn main() { fn main() {
let mut buffer = String::new(); let mut buffer = String::new();
@ -13,7 +13,8 @@ fn main() {
.map(|digit| i32::from_str(&digit).unwrap()) .map(|digit| i32::from_str(&digit).unwrap())
.collect::<Vec<_>>(); .collect::<Vec<_>>();
println!("{}", redistribution_cycles(&mut banks)); let result = redistribution_cycles(&mut banks);
println!("cycles = {}\nsize of loop = {}", result.0, result.1);
} }
fn redistribute(banks: &mut Vec<i32>) { fn redistribute(banks: &mut Vec<i32>) {
@ -30,22 +31,25 @@ fn redistribute(banks: &mut Vec<i32>) {
} }
} }
fn redistribution_cycles(banks: &mut Vec<i32>) -> usize { fn redistribution_cycles(banks: &mut Vec<i32>) -> (usize, usize) {
let mut seen_states = HashSet::new(); let mut seen_states = HashMap::new();
seen_states.insert(banks.clone()); let mut loop_count: usize = 0;
seen_states.insert(banks.clone(), loop_count);
loop { loop {
redistribute(banks); redistribute(banks);
if seen_states.insert(banks.clone()) == false { loop_count += 1;
break; if let Some(&seen_at_loop) = seen_states.get(banks) {
return (seen_states.len(), loop_count - seen_at_loop);
}
else {
seen_states.insert(banks.clone(), loop_count);
} }
} }
seen_states.len()
} }
#[test] #[test]
fn test_example() { fn test_example() {
let mut banks = vec![0, 2, 7, 0]; let mut banks = vec![0, 2, 7, 0];
assert_eq!(redistribution_cycles(&mut banks), 5); assert_eq!(redistribution_cycles(&mut banks), (5, 4));
} }