Day 2

2024/day2/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day2"
+version = "0.1.0"

2024/day2/Cargo.toml

@@ -0,0 +1,6 @@
+[package]
+name = "day2"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]

2024/day2/src/main.rs

@@ -0,0 +1,87 @@
+fn read_input() -> Vec<Vec<i32>> {
+    let string = std::fs::read_to_string("./input.txt").unwrap();
+    string
+        .lines()
+        .map(|line| {
+            line.split_whitespace()
+                .map(|val| val.parse().unwrap())
+                .collect()
+        })
+        .collect()
+}
+
+fn is_safe(report: &Vec<i32>) -> bool {
+    let mut last_value = report[0];
+    let mut increment = 0;
+    // the current increment between two values. Mainly for tracking the direction of travel of the series
+    for current_value in report.iter().skip(1) {
+        let difference = current_value - last_value;
+        if increment * difference < 0 // i.e. difference & increment have different signs
+            || difference.abs() < 1
+            || difference.abs() > 3
+        {
+            return false;
+        }
+        last_value = *current_value;
+        increment = difference;
+    }
+    true
+}
+
+fn task1() {
+    let reports = read_input();
+    let mut safe_reports = 0;
+    let mut unsafe_reports = 0;
+    for report in reports.iter() {
+        if is_safe(report) {
+            safe_reports += 1;
+        } else {
+            unsafe_reports += 1;
+        }
+    }
+
+    println!(
+        "Task1: Total reports: {}, safe: {}, unsafe: {}",
+        reports.iter().len(),
+        safe_reports,
+        unsafe_reports
+    );
+}
+
+fn task2() {
+    let reports = read_input();
+    let mut safe_reports = 0;
+    let mut unsafe_reports = 0;
+    let total = reports.len();
+    for report in reports.into_iter() {
+        if is_safe(&report) {
+            safe_reports += 1;
+        } else {
+            // check whether any value being left out makes it safe
+            let has_safe = 'safe_check: {
+                for ignore_idx in 0..report.len() {
+                    let mut modified_report = report.clone();
+                    modified_report.splice(ignore_idx..ignore_idx + 1, []);
+                    if is_safe(&modified_report) {
+                        safe_reports += 1; // if there's one version how to make it safe, we're good
+                        break 'safe_check true;
+                    }
+                }
+                false // couldn't find a safe report
+            };
+            if !has_safe {
+                unsafe_reports += 1;
+            }
+        }
+    }
+
+    println!(
+        "Task2: Total reports: {}, safe: {}, unsafe: {}",
+        total, safe_reports, unsafe_reports
+    );
+}
+
+fn main() {
+    task1();
+    task2();
+}