Day 3 - Part 1

Signed-off-by: Anthony Oteri <anthony.oteri@gmail.com>

day-03/src/main.rs

@@ -0,0 +1,169 @@
+use std::collections::BTreeMap;
+
+#[derive(Debug, Clone)]
+enum Value {
+    Digit(u32),
+    Symbol(char),
+}
+
+#[derive(Debug, Clone, Default, PartialOrd, Ord, Eq, PartialEq)]
+struct Address {
+    row: i32,
+    col: i32,
+}
+
+fn part_1(input: &str) -> u32 {
+    let numbers = input
+        .lines()
+        .enumerate()
+        .flat_map(|(row, line)| {
+            extract_numbers(line)
+                .into_iter()
+                .map(move |(col, len, number)| {
+                    (
+                        (col..col + len)
+                            .map(|c| Address {
+                                row: row as i32,
+                                col: c as i32,
+                            })
+                            .collect::<Vec<_>>(),
+                        number,
+                    )
+                })
+        })
+        .collect::<Vec<(Vec<Address>, u32)>>();
+
+    let grid = input
+        .lines()
+        .enumerate()
+        .flat_map(|(row, line)| {
+            line.chars().enumerate().map(move |(col, character)| {
+                (
+                    Address {
+                        row: row as i32,
+                        col: col as i32,
+                    },
+                    match character {
+                        '.' => None,
+                        c if c.is_ascii_digit() => Some(Value::Digit(c.to_digit(10).unwrap())),
+                        c => Some(Value::Symbol(c)),
+                    },
+                )
+            })
+        })
+        .collect::<BTreeMap<Address, Option<Value>>>();
+
+    let symbols: BTreeMap<Address, char> = grid
+        .iter()
+        .filter_map(|(address, value)| match value {
+            Some(Value::Symbol(c)) => Some((address.clone(), *c)),
+            _ => None,
+        })
+        .collect();
+
+    let mut sum = 0;
+    for (addresses, number) in numbers {
+        if addresses
+            .iter()
+            .flat_map(bounding_box)
+            .any(|a| symbols.contains_key(&a))
+        {
+            sum += number;
+        }
+    }
+
+    sum
+}
+
+fn extract_numbers(input: &str) -> Vec<(usize, usize, u32)> {
+    let mut result = Vec::default();
+    let mut current_number = String::new();
+    let mut current_offset = 0;
+
+    for (offset, c) in input.chars().enumerate() {
+        if c.is_ascii_digit() {
+            current_number.push(c);
+            current_offset = offset + 1;
+        } else if !current_number.is_empty() {
+            result.push((
+                current_offset - current_number.len(),
+                current_number.len(),
+                current_number.parse::<u32>().unwrap(),
+            ));
+            current_number.clear();
+        }
+    }
+
+    if !current_number.is_empty() {
+        result.push((
+            current_offset - current_number.len(),
+            current_number.len(),
+            current_number.parse::<u32>().unwrap(),
+        ));
+    }
+
+    result
+}
+
+fn bounding_box(address: &Address) -> Vec<Address> {
+    vec![
+        Address {
+            row: address.row - 1,
+            col: address.col - 1,
+        },
+        Address {
+            row: address.row - 1,
+            col: address.col,
+        },
+        Address {
+            row: address.row - 1,
+            col: address.col + 1,
+        },
+        Address {
+            row: address.row,
+            col: address.col - 1,
+        },
+        Address {
+            row: address.row,
+            col: address.col + 1,
+        },
+        Address {
+            row: address.row + 1,
+            col: address.col - 1,
+        },
+        Address {
+            row: address.row + 1,
+            col: address.col,
+        },
+        Address {
+            row: address.row + 1,
+            col: address.col + 1,
+        },
+    ]
+}
+
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("Part 1: {}", part_1(input));
+}
+
+#[cfg(test)]
+mod test {
+    use std::vec;
+
+    use super::*;
+
+    #[test]
+    fn test_extract_number() {
+        assert_eq!(
+            extract_numbers("123..45.6"),
+            vec![(0, 3, 123), (5, 2, 45), (8, 1, 6)]
+        );
+    }
+
+    #[test]
+    fn test_part1() {
+        let input = include_str!("../test-input.txt");
+        assert_eq!(part_1(input), 4361);
+    }
+}