Add day2

2024/day2/src/main.rs

@@ -0,0 +1,61 @@
+use std::{collections::HashSet, fs};
+
+fn main() {
+    let file = fs::read_to_string("./input.txt").unwrap();
+    let mut rows = Vec::new();
+
+    for line in file.lines() {
+        let vals = line
+            .split_whitespace()
+            .map(|x| x.parse::<i32>().unwrap())
+            .collect::<Vec<i32>>();
+
+        rows.push(vals);
+    }
+
+    println!("Solution 1: {}", puzzle1(rows.clone()));
+    println!("Solution 2: {}", puzzle2(rows));
+}
+
+fn puzzle1(rows: Vec<Vec<i32>>) -> i32 {
+    let mut counter = 0;
+    for r in rows {
+        if is_safe(&r) {
+            counter += 1;
+        }
+    }
+    counter
+}
+
+fn puzzle2(rows: Vec<Vec<i32>>) -> i32 {
+    let mut counter = 0;
+    for r in rows {
+        if is_safe(&r) {
+            counter += 1;
+            continue;
+        }
+
+        for i in 0..r.len() {
+            let mut modrow = r.clone();
+            modrow.remove(i);
+            if is_safe(&modrow) {
+                counter += 1;
+                break;
+            }
+        }
+    }
+    counter
+}
+
+fn is_safe(row: &[i32]) -> bool {
+    let mut safeslopes: HashSet<i32> = HashSet::from_iter(vec![1, 2, 3]);
+    let mut safenegslopes: HashSet<i32> = HashSet::from_iter(vec![-1, -2, -3]);
+
+    for i in 1..row.len() {
+        let diff = row[i] - row[i - 1];
+        safeslopes.insert(diff);
+        safenegslopes.insert(diff);
+    }
+
+    safeslopes.len() == 3 || safenegslopes.len() == 3
+}