Cleanup, remove unnecessary allocationss, etc.

2024/rust/src/day2.rs

@@ -16,73 +16,61 @@ impl FromStr for Report {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         let levels = s
             .split(" ")
-            .filter(|s| !s.is_empty())
             .map(|s| s.parse())
             .collect::<Result<Vec<i64>, ParseIntError>>()?;
         Ok(Self { levels })
     }
 }
 
-#[derive(PartialEq, Eq)]
-enum LevelSafeKind {
-    Increasing,
-    Decreasing,
-}
-
 impl Report {
-    fn is_safe(&self) -> bool {
-        Self::is_level_set_safe(&self.levels)
-    }
+    fn is_safe(&self, skip_index: Option<usize>) -> bool {
+        let mut ordering: Option<Ordering> = None;
+        let skip_index = skip_index.unwrap_or(self.levels.len() + 1);
+        let max = if skip_index < self.levels.len() {
+            self.levels.len() - 2
+        } else {
+            self.levels.len() - 1
+        };
 
-    fn is_level_set_safe(levels: &[i64]) -> bool {
-        let mut iter = levels.windows(2);
-        let mut level_safe_kind: Option<LevelSafeKind> = None;
-
-        while let Some(&[a, b]) = iter.next() {
-            if !Self::safe_level_pair(a, b, &level_safe_kind) {
+        for i in 0..max {
+            let mut ai = i;
+            let mut bi = ai + 1;
+            if ai >= skip_index {
+                ai += 1
+            };
+            if bi >= skip_index {
+                bi += 1
+            };
+            let (a, b) = (self.levels[ai], self.levels[bi]);
+            if !Self::safe_level_pair(a, b, &ordering) {
                 return false;
             }
-            if level_safe_kind == None {
-                if a > b {
-                    level_safe_kind = Some(LevelSafeKind::Increasing)
-                } else {
-                    level_safe_kind = Some(LevelSafeKind::Decreasing)
-                }
+            if ordering == None {
+                ordering = Some(a.cmp(&b))
             }
         }
+
         return true;
     }
 
     fn is_safe_with_any_single_level_removed(&self) -> bool {
-        // TODO: this allocates for each level combination and so is suboptimal
-        // best solution I think is to update is_level_set_safe to take index pairs or something and slide those in such a way that we skip one of the indices
         for i in 0..self.levels.len() {
-            let levels: Vec<i64> = self
-                .levels
-                .clone()
-                .iter()
-                .enumerate()
-                .filter(|&(index, _val)| i != index)
-                .map(|(_index, val)| *val)
-                .collect();
-            if Self::is_level_set_safe(&levels) {
+            if i > 0 {}
+            if self.is_safe(Some(i)) {
                 return true;
             }
         }
         return false;
     }
 
-    fn safe_level_pair(a: i64, b: i64, kind: &Option<LevelSafeKind>) -> bool {
+    fn safe_level_pair(a: i64, b: i64, kind: &Option<Ordering>) -> bool {
         if a == b {
             return false;
         }
         if (a - b).abs() > 3 {
             return false;
         }
-        if a - b < 0 && *kind == Some(LevelSafeKind::Increasing) {
-            return false;
-        }
-        if a - b > 0 && *kind == Some(LevelSafeKind::Decreasing) {
+        if kind.map(|o| o == a.cmp(&b)) == Some(false) {
             return false;
         }
         return true;
@@ -107,7 +95,7 @@ impl FromStr for Data {
 
 impl Data {
     fn num_safe(&self) -> usize {
-        self.reports.iter().filter(|r| r.is_safe()).count()
+        self.reports.iter().filter(|r| r.is_safe(None)).count()
     }
 
     fn num_safe_with_dampener(&self) -> usize {
@@ -124,7 +112,7 @@ mod tests {
 
     #[test]
     fn test() {
-        let mut report: Data = "7 6 4 2 1
+        let data: Data = "7 6 4 2 1
 1 2 7 8 9
 9 7 6 2 1
 1 3 2 4 5
@@ -132,8 +120,18 @@ mod tests {
 1 3 6 7 9"
             .parse()
             .unwrap();
-        assert_eq!(report.num_safe(), 2);
-        assert_eq!(report.num_safe_with_dampener(), 4);
+        assert_eq!(data.num_safe(), 2);
+        assert_eq!(data.num_safe_with_dampener(), 4);
+        // assert_eq!(report.(), 31);
+    }
+
+    #[test]
+    fn test2() {
+        let report: Report = Report {
+            levels: vec![1, 2, 5, 8, 9, 15],
+        };
+        assert_eq!(report.is_safe(None), false);
+        assert_eq!(report.is_safe_with_any_single_level_removed(), true);
         // assert_eq!(report.(), 31);
     }
 }

2024/rust/src/prelude.rs

@@ -1,5 +1,6 @@
 use std::path::{Path, PathBuf};
 pub use std::{
+    cmp::Ordering,
     collections::HashMap,
     fs::File,
     io::Read,