add 03

lib/aoc/src/lib.rs

@@ -6,3 +6,12 @@ pub fn read_file(filename: &str) -> Vec<String> {
     f.read_to_string(&mut buffer).unwrap();
     buffer.lines().map(|s| s.to_owned()).collect()
 }
+
+pub fn read_grid(filename: &str) -> Vec<Vec<char>> {
+    let result = read_file(filename)
+        .into_iter()
+        .map(|line| line.chars().collect())
+        .collect();
+
+    result
+}