days 1-3

day03/Cargo.lock

@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "day03"
+version = "0.1.0"

day03/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day03"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day03/src/main.rs

@@ -0,0 +1,114 @@
+use std::collections::HashMap;
+use std::io::{stdin, BufRead};
+
+type Point = (usize, usize);
+const EMPTY_SYMBOL: char = '.';
+const GEAR_SYMBOL: char = '*';
+const DEFAULT_POINT: Point = (usize::MAX, usize::MAX);
+
+fn main() {
+    let input = stdin()
+        .lock()
+        .lines()
+        .map(|l| l.unwrap().chars().collect::<Vec<_>>())
+        .collect::<Vec<_>>();
+
+    let mut sum = 0;
+    let mut gear_surrounding_nums: HashMap<Point, Vec<usize>> = HashMap::new();
+
+    for (y, row) in input.iter().enumerate() {
+        let mut current_num = String::new();
+        let mut valid = false;
+        let mut gear_pos = DEFAULT_POINT;
+
+        for (x, col) in row.iter().enumerate() {
+            if col.is_ascii_digit() {
+                current_num.push(*col);
+                let points = points_around(x, y);
+
+                for point in points {
+                    if let Some(adjacent_symbol) = get_at_point(point.0, point.1, &input) {
+                        if !adjacent_symbol.is_ascii_digit() && adjacent_symbol != &EMPTY_SYMBOL {
+                            valid = true;
+                        }
+                        if adjacent_symbol == &GEAR_SYMBOL {
+                            gear_pos = point;
+                        }
+                    }
+                }
+            } else if !current_num.is_empty() {
+                check_and_update_point(
+                    valid,
+                    &current_num,
+                    &mut sum,
+                    &gear_pos,
+                    &mut gear_surrounding_nums,
+                );
+                gear_pos = DEFAULT_POINT;
+                valid = false;
+                current_num.clear();
+            }
+        }
+        check_and_update_point(
+            valid,
+            &current_num,
+            &mut sum,
+            &gear_pos,
+            &mut gear_surrounding_nums,
+        );
+    }
+
+    let part2 = gear_surrounding_nums
+        .iter()
+        .filter_map(|gear| match gear.1.len() == 2 {
+            true => Some(gear.1),
+            _ => None,
+        })
+        .fold(0, |total, gear_vals| {
+            total + gear_vals.iter().product::<usize>()
+        });
+
+    println!("P1: {} P2: {}", sum, part2);
+}
+
+fn check_and_update_point(
+    valid: bool,
+    current_num: &str,
+    sum: &mut usize,
+    gear_pos: &Point,
+    gear_surrounding_nums: &mut HashMap<Point, Vec<usize>>,
+) {
+    if valid {
+        let numeric_val = current_num.parse::<usize>().unwrap();
+
+        *sum += numeric_val;
+        if *gear_pos != DEFAULT_POINT {
+            let gears = gear_surrounding_nums.get_mut(gear_pos);
+            if let Some(gear_vec) = gears {
+                gear_vec.push(numeric_val);
+            } else {
+                gear_surrounding_nums.insert(*gear_pos, vec![numeric_val]);
+            }
+        }
+    }
+}
+
+fn get_at_point(x: usize, y: usize, grid: &[Vec<char>]) -> Option<&char> {
+    if let Some(row) = grid.get(y) {
+        return row.get(x);
+    }
+    None
+}
+
+fn points_around(x: usize, y: usize) -> Vec<Point> {
+    let mut points = Vec::new();
+    for i in x.saturating_sub(1)..(x + 2) {
+        for j in y.saturating_sub(1)..(y + 2) {
+            if (i, j) == (x, y) {
+                continue;
+            }
+            points.push((i, j));
+        }
+    }
+    points
+}