diff --git a/2023/day3/src/example_input.txt b/2023/day3/src/example_input.txt
new file mode 100644
index 0000000..624ea4f
--- /dev/null
+++ b/2023/day3/src/example_input.txt
@@ -0,0 +1,10 @@
+467..114..
+...*......
+..35..633.
+......#...
+617*......
+.....+.58.
+..592.....
+......755.
+...$.*....
+.664.598..
\ No newline at end of file
diff --git a/2023/day3/src/main.rs b/2023/day3/src/main.rs
index ec277e9..6bb6c82 100644
--- a/2023/day3/src/main.rs
+++ b/2023/day3/src/main.rs
@@ -1,10 +1,223 @@
+use crate::ValueType::Number;
+use std::collections::HashSet;
+use std::ops::Range;
+
 const FILE_STR: &'static str = include_str!("input.txt");
 
+#[derive(Debug, Default)]
+struct NumberLocation {
+    start: usize,
+    end: usize,
+    digits: String,
+}
+
+impl NumberLocation {
+    fn new(start: usize, value: char) -> Self {
+        NumberLocation {
+            start,
+            end: start + 1,
+            digits: String::from(value),
+        }
+    }
+
+    fn add_digit(&mut self, digit: char) {
+        self.end += 1;
+        self.digits.push(digit);
+    }
+
+    fn to_number(&self) -> usize {
+        self.digits.parse::<usize>().unwrap()
+    }
+}
+
+#[derive(Debug, Copy, Clone, PartialOrd, PartialEq, Eq, Hash)]
+enum ValueType {
+    Number(usize),
+    Symbol,
+    Empty,
+}
+
+#[derive(Debug, Default)]
+struct Grid {
+    line_size: usize,
+    numbers: Vec<NumberLocation>,
+    values: Vec<ValueType>,
+}
+
+impl Grid {
+    pub fn parse(input_str: &str) -> Self {
+        let len = input_str.split('\n').next().unwrap().len();
+        let mut values: Vec<ValueType> = Vec::new();
+        let mut numbers: Vec<NumberLocation> = Vec::new();
+        let chars: Vec<char> = input_str.replace("\n", "").chars().collect();
+        let mut prev = ValueType::Empty;
+        chars.iter().enumerate().for_each(|(i, ch)| {
+            if ch.is_digit(10) {
+                if let Number(_) = prev {
+                    let final_num = { numbers.len() - 1 };
+                    numbers.get_mut(final_num).unwrap().add_digit(*ch);
+                } else {
+                    let nl = NumberLocation::new(i, *ch);
+                    numbers.push(nl);
+                }
+
+                prev = Number(numbers.len() - 1);
+            } else if *ch == '.' {
+                prev = ValueType::Empty;
+            } else {
+                prev = ValueType::Symbol;
+            }
+
+            values.push(prev);
+        });
+
+        Grid {
+            line_size: len,
+            numbers,
+            values,
+        }
+    }
+
+    pub fn num_cols(&self) -> usize {
+        self.line_size
+    }
+
+    pub fn num_rows(&self) -> usize {
+        self.values.len() / self.num_cols()
+    }
+
+    // Convert x,y coordinate into linear array index
+    pub fn xy_idx(&self, x: usize, y: usize) -> usize {
+        (y * self.num_cols()) + x
+    }
+
+    /// Convert linear array index to x,y coordinate
+    pub fn idx_xy(&self, idx: usize) -> (usize, usize) {
+        (idx % self.num_cols(), idx / self.num_cols())
+    }
+
+    fn adjacent_ind(&self, i: usize) -> HashSet<usize> {
+        let mut ind = HashSet::new();
+        if i >= self.values.len() {
+            return ind;
+        }
+
+        // Forwards/backwards
+        if i > 0 {
+            ind.insert(i - 1);
+        }
+        if i + 1 < self.values.len() {
+            ind.insert(i + 1);
+        }
+
+        // Row above/below
+        let (col, row) = self.idx_xy(i);
+        if row + 1 < self.num_rows() {
+            ind.insert(self.xy_idx(col, row + 1));
+        }
+        if row > 0 {
+            ind.insert(self.xy_idx(col, row - 1));
+        }
+
+        // Diagonals (x+1, y-1),(x-1, y-1),(x+1, y+1),(x-1,y+1)
+        if col > 0 && row > 0 {
+            ind.insert(self.xy_idx(col - 1, row - 1));
+        }
+        if col > 0 && row + 1 < self.num_rows() {
+            ind.insert(self.xy_idx(col - 1, row + 1));
+        }
+        if col + 1 < self.num_cols() && row > 0 {
+            ind.insert(self.xy_idx(col + 1, row - 1));
+        }
+        if col + 1 < self.num_cols() && row + 1 < self.num_rows() {
+            ind.insert(self.xy_idx(col + 1, row + 1));
+        }
+
+        ind
+    }
+
+    fn find_adjacent(&self, r: Range<usize>) -> Vec<ValueType> {
+        let mut adj = Vec::new();
+
+        for i in r {
+            self.adjacent_ind(i)
+                .into_iter()
+                .for_each(|ind| adj.push(self.values[ind]));
+        }
+
+        adj
+    }
+
+    fn is_part_number(&self, r: Range<usize>) -> bool {
+        self.find_adjacent(r).contains(&ValueType::Symbol)
+    }
+
+    fn get_part_numbers(&self) -> Vec<usize> {
+        self.numbers
+            .iter()
+            .filter(|nl| {
+                let range = nl.start..nl.end;
+                self.is_part_number(range)
+            })
+            .map(|nl| nl.to_number())
+            .collect()
+    }
+
+    fn get_part_number_sum(&self) -> usize {
+        self.numbers
+            .iter()
+            .filter(|nl| {
+                let range = nl.start..nl.end;
+                self.is_part_number(range)
+            })
+            .map(|nl| nl.to_number())
+            .sum()
+    }
+}
+
+fn part_one() {
+    let grid = Grid::parse(FILE_STR);
+    println!(
+        "Part 1: Sum of part numbers: {}",
+        grid.get_part_number_sum()
+    );
+}
+
 fn main() {
-    println!("Hello, world!");
+    part_one();
 }
 
 #[cfg(test)]
 mod tests {
+    use std::iter::FromIterator;
+
+    const EXAMPLE_FILE_STR: &'static str = include_str!("example_input.txt");
     use super::*;
-}
\ No newline at end of file
+
+    #[test]
+    fn test_adjacent_index() {
+        let grid = Grid::parse(EXAMPLE_FILE_STR);
+        assert_eq!(grid.adjacent_ind(5), HashSet::from([4, 6, 14, 15, 16]));
+    }
+
+    #[test]
+    fn test_find_adjacent() {
+        let grid = Grid::parse(EXAMPLE_FILE_STR);
+        let adjacent = grid.find_adjacent(5..6);
+        let hadj = HashSet::from_iter(adjacent.iter().cloned());
+        assert_eq!(hadj, HashSet::from([ValueType::Empty, Number(1)]));
+    }
+
+    #[test]
+    fn test_get_part_numbers() {
+        let grid = Grid::parse(EXAMPLE_FILE_STR);
+        let expected = [467, 35, 633, 617, 592, 755, 664, 598];
+        assert_eq!(grid.get_part_numbers(), expected);
+    }
+
+    #[test]
+    fn test_part_number_sum() {
+        let grid = Grid::parse(EXAMPLE_FILE_STR);
+        assert_eq!(grid.get_part_number_sum(), 4361);
+    }
+}