Day 5: Mutating strings

1 files changed, 36 insertions, 1 deletions

diff --git a/src/bin/day_5.rs b/src/bin/day_5.rs
index 1129e3a..d689e34 100644
--- a/src/bin/day_5.rs
+++ b/src/bin/day_5.rs
@@ -3,16 +3,51 @@ use advent_of_code_2018::*;
 
 use std::error::Error;
 use std::path::PathBuf;
+use std::cmp;
 
 // cargo watch -cs "cargo run --release --bin day_5"
 
 fn main() -> Result<(), Box<Error>> {
     let input = read_file(&PathBuf::from("inputs/5.txt"))?;
 
-    println!("Input: {:?}", input);
+    //println!("Input: {:?}", input);
+    let polymer = {
+        let mut polymer: Vec<char> = input[0].chars().collect();
+        reduce(&mut polymer);
+        polymer
+    };
 
+    println!("Base length after reducing: {}", polymer.len());
 
 
+    let mut min_length = polymer.len();
+    for c in "abcdefghijklmnopqrstuvwxyz".chars() {
+        let mut polymer_without_char = polymer.clone();
+        polymer_without_char.retain(|x| x.to_ascii_lowercase() != c);
+        reduce(&mut polymer_without_char);
+        min_length = cmp::min(min_length, polymer_without_char.len());
+    }
+
+    println!("Minimum length found: {}", min_length);
 
     Ok(())
 }
+
+
+fn reduce(polymer: &mut Vec<char>) {
+    let mut had_reductions = true;
+    while had_reductions {
+        had_reductions = false;
+        
+        for i in 0..polymer.len()-1 {
+            if polymer[i].to_ascii_lowercase() == polymer[i+1].to_ascii_lowercase() && polymer[i] != polymer[i+1] {
+                had_reductions = true;
+                polymer.remove(i+1);
+                polymer.remove(i);
+
+                // break isn't efficient, but does prevent indexing issues after removing
+                break;
+            }
+        }
+    }
+}