add: files so far

d/d2p2.rs

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+use advent_of_code_2024::{make_main, SResult};
+
+make_main!();
+
+#[derive(PartialEq, Clone, Copy)]
+enum Direction {
+    Up,
+    Down,
+}
+
+impl Direction {
+    fn from(a: usize, b: usize) -> Self {
+        if a > b {
+            Direction::Down
+        } else {
+            Direction::Up
+        }
+    }
+}
+
+fn solve(lines: Vec<String>) -> SResult<usize> {
+    let mut fail_count = 0;
+    for line in lines.iter() {
+        let reports: Vec<usize> = line
+            .split_whitespace()
+            .map(|v| v.parse::<usize>().unwrap())
+            .collect();
+        let problems = match test(&reports) {
+            // Cool, nothing to see here
+            Ok(_) => continue,
+            Err(e) => e,
+        };
+        let mut pass = false;
+        for problem in problems {
+            let mut l1 = reports.clone();
+            l1.remove(problem);
+            if test(&l1).is_ok() {
+                pass = true;
+                break;
+            }
+        }
+        if !pass {
+            fail_count += 1;
+        }
+    }
+    Ok(lines.len() - fail_count)
+}
+
+// Tests the report, and returns indexes around where a failure is detected.
+fn test(reports: &[usize]) -> Result<(), Vec<usize>> {
+    let mut i = 0;
+    let direction = Direction::from(reports[0], reports[1]);
+    while i + 1 < reports.len() {
+        let delta = reports[i].abs_diff(reports[i + 1]);
+        if delta < 1 || delta > 3 || direction != Direction::from(reports[i], reports[i + 1]) {
+            let mut errs = vec![i, i + 1];
+            if i > 0 {
+                errs.push(i - 1);
+            }
+            return Err(errs);
+        }
+        i += 1;
+    }
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use advent_of_code_2024::input;
+
+    use super::*;
+    #[test]
+    fn sample_input() {
+        let strings: Vec<String> = input!("d2p1.txt");
+        let got = solve(strings).unwrap();
+        assert_eq!(got, 4);
+    }
+}