Better report safety checking

day_02/src/main.rs

@@ -1,4 +1,7 @@
-use std::collections::HashMap;
+// https://adventofcode.com/2024/day/2
+//
+// run command: `cargo run ./input.txt`
+
 use std::env;
 use std::error::Error;
 use std::fs::File;
@@ -17,42 +20,81 @@ where
     Ok(parsed_line)
 }
 
-enum ReportDirection {
+#[derive(Eq, PartialEq)]
+enum LevelTransitionState {
     Asc,
     Desc,
+    Bad,
+    Dampened,
 }
 
-fn is_report_safe(report: &Vec<i64>) -> bool {
-    let direction = if report[0] < report[1] {
-        ReportDirection::Asc
-    } else {
-        ReportDirection::Desc
-    };
+fn compare_levels(curr_level: i64, next_level: i64) -> LevelTransitionState {
+    let level_diff = next_level - curr_level;
 
-    match direction {
-        ReportDirection::Asc => {
-            let mut prev_report_level = report[0];
-            for report_level in report[1..].iter() {
-                if prev_report_level >= *report_level || report_level - prev_report_level > 3 {
-                    return false;
-                }
-                prev_report_level = *report_level;
-            }
-        }
-        ReportDirection::Desc => {
-            let mut prev_report_level = report[0];
-            for report_level in report[1..].iter() {
-                if prev_report_level <= *report_level || prev_report_level - report_level > 3 {
-                    return false;
-                }
-                prev_report_level = *report_level;
-            }
-        }
-    };
-
-    true
+    // If the diff is 0 or greater than 3, return bad stat
+    if level_diff == 0 || level_diff.abs() > 3 {
+        return LevelTransitionState::Bad;
+    }
+    // If great than zero they are ascending
+    if level_diff > 0 {
+        return LevelTransitionState::Asc;
+    }
+    //Else we're descending
+    return LevelTransitionState::Desc;
 }
 
+fn is_report_safe(report: Vec<i64>) -> bool {
+    // Turn the report into a bunch of states for each adjacent pair in the report
+    let report: Vec<LevelTransitionState> = report
+        .windows(2)
+        .map(|l| compare_levels(l[0], l[1]))
+        .collect();
+
+    // Setup the loop by checking the first start as a special case
+    let mut prev_state = &report[0];
+    if prev_state == &LevelTransitionState::Bad {
+        return false;
+    }
+
+    // Check each state
+    for level_state in report[1..].iter() {
+        // If bad, then it's just bad
+        if level_state == &LevelTransitionState::Bad {
+            return false;
+        }
+
+        // If the states aren't the same as the prev, it must
+        // have changed direction
+        if level_state != prev_state {
+            return false;
+        }
+
+        // Setup for next iteration
+        prev_state = level_state;
+    }
+    return true;
+}
+
+// let mut modified_report: Vec<Option<i64>> = vec![None];
+// let mut tmp_report: Vec<Option<i64>> = report.iter().map(|v| Some(*v)).collect();
+// modified_report.append(&mut tmp_report);
+// modified_report.push(None);
+// dbg!(modified_report);
+
+// let states = Vec::new();
+// for window in modified_report.windows(3) {
+//     let window_tuple = (window[0], window[1], window[2]);
+//     let state = match window_tuple {
+//         (None, Some(curr), Some(next)) => {
+//             let diff = curr
+//         },
+//         (Some(prev), Some(curr), Some(next)) => (),
+//         (Some(prev), Some(curr), None) => (),
+//         _ => panic!("This should never happen!"),
+//     }
+//     states.push(state);
+// }
+
 fn main() -> Result<(), Box<dyn Error>> {
     // Handle command input
     let args: Vec<String> = env::args().collect();
@@ -71,7 +113,7 @@ fn main() -> Result<(), Box<dyn Error>> {
     for line in input_reader.lines() {
         let line = line?;
         let parsed_report: Vec<i64> = parse_report(&line)?;
-        if is_report_safe(&parsed_report) {
+        if is_report_safe(parsed_report) {
             accumulator += 1;
         }
     }