day 9 cleanup

src/day09.rs

@@ -1,7 +1,5 @@
 use std::{collections::BTreeMap, fs::read_to_string};
 
-use itertools::Itertools;
-
 pub fn day_main() {
     let input = read_to_string("input/day09.txt").unwrap();
     let input = input.trim();
@@ -55,8 +53,8 @@ fn part1(input: &str) -> RiddleResult {
 }
 
 fn part2(input: &str) -> RiddleResult {
-    // (start_index, len, file_id)
     let mut free: BTreeMap<usize, usize> = BTreeMap::new();
+    // (start_index, len, file_id)
     let mut files: Vec<(usize, usize, usize)> = Vec::with_capacity(input.len() / 2 + 1);
     let mut head = 0;
     for (i, l) in input.chars().enumerate() {
@@ -70,13 +68,15 @@ fn part2(input: &str) -> RiddleResult {
     }
     for file in files.iter_mut().rev() {
         let (start_index, length, _file_id) = *file;
-        let found = free.iter().find(|f| *f.1 >= length && *f.0 < start_index);
+        let found = free
+            .iter()
+            .take_while(|f| *f.0 < start_index)
+            .find(|f| *f.1 >= length);
 
         if let Some((&free_start, &free_length)) = found.clone() {
             free.remove(&free_start);
             free.insert(start_index, length);
             file.0 = free_start;
-            merge(&mut free, start_index);
             if length < free_length {
                 free.insert(free_start + length, free_length - length);
             }
@@ -91,34 +91,8 @@ fn part2(input: &str) -> RiddleResult {
         .sum()
 }
 
-fn merge(free: &mut BTreeMap<usize, usize>, start_index: usize) {
-    let mut current = start_index;
-    if let Some((&left, &left_length)) = free.range(0..start_index).last() {
-        if left + left_length == start_index {
-            *free.get_mut(&left).unwrap() += free.remove(&start_index).unwrap();
-            current = left;
-        }
-    }
-    if current == *free.last_entry().unwrap().key() {
-        return; // make sure we don't try to access a range starting > max, panics
-    }
-    if let Some((&right, &_right_length)) = free.range(current + 1..).next() {
-        if current + free[&current] == right {
-            *free.get_mut(&current).unwrap() += free.remove(&right).unwrap();
-        }
-    }
-}
-
-fn n(m: usize) -> usize {
-    (m * m - m) / 2
-}
-
 #[cfg(test)]
 mod test {
-    use std::collections::BTreeMap;
-
-    use crate::day09::merge;
-
     use super::{part1, part2};
 
     const TEST_INPUT: &str = r"2333133121414131402";
@@ -132,35 +106,4 @@ mod test {
     fn test2() {
         assert_eq!(part2(TEST_INPUT), 2858);
     }
-
-    #[test]
-    fn merge_left() {
-        let mut tree = BTreeMap::new();
-        tree.insert(0, 3);
-        tree.insert(3, 5);
-        merge(&mut tree, 3);
-        assert_eq!(tree.len(), 1);
-        assert_eq!(tree[&0], 8);
-    }
-
-    #[test]
-    fn merge_right() {
-        let mut tree = BTreeMap::new();
-        tree.insert(0, 3);
-        tree.insert(3, 5);
-        merge(&mut tree, 0);
-        assert_eq!(tree.len(), 1);
-        assert_eq!(tree[&0], 8);
-    }
-
-    #[test]
-    fn merge_both() {
-        let mut tree = BTreeMap::new();
-        tree.insert(0, 3);
-        tree.insert(3, 5);
-        tree.insert(8, 11);
-        merge(&mut tree, 3);
-        assert_eq!(tree.len(), 1);
-        assert_eq!(tree[&0], 19);
-    }
 }