add day 9 part 1

day09/src/main.rs

@@ -0,0 +1,105 @@
+fn main() {
+    let data = std::fs::read_to_string("input.txt").unwrap();
+
+    part1(data.trim()); // 150914
+    part2(data.trim());
+}
+
+fn part2(data: &str) {
+    // let mut input = data.to_string();
+
+    // while input.contains('(') {
+    //     input = decompress_sequence(&input);
+    // }
+    // println!("{}", input.len());
+}
+
+fn part1(data: &str) {
+    let result = decompress_sequence(data).len();
+
+    println!("{result}");
+}
+
+fn decompress_sequence(s: &str) -> String {
+    let mut result: Vec<_> = vec![];
+
+    let mut pointer = 0;
+
+    let s_chars: Vec<_> = s.chars().collect();
+
+    while let Some(c) = s_chars.get(pointer) {
+        if *c == '(' {
+            let (repeat_length, repeat_amount, marker_length) = parse_marker(&s_chars, &pointer);
+
+            let substring: Vec<_> = s
+                [pointer + marker_length..pointer + marker_length + repeat_length]
+                .chars()
+                .collect();
+            for _ in 0..repeat_amount {
+                for c in &substring {
+                    result.push(*c);
+                }
+            }
+            pointer += marker_length + repeat_length;
+        } else {
+            result.push(*c);
+            pointer += 1;
+        }
+    }
+
+    result.iter().collect()
+}
+
+fn parse_marker(s: &[char], pointer: &usize) -> (usize, usize, usize) {
+    let chars: Vec<_> = s[*pointer + 1..]
+        .iter()
+        .take_while(|c| **c != ')')
+        .collect();
+    let mut split = chars.split(|c| **c == 'x');
+
+    let length: String = split.next().unwrap().iter().cloned().collect();
+    let amount: String = split.next().unwrap().iter().cloned().collect();
+
+    let marker_length = 1 + length.len() + 1 + amount.len() + 1;
+
+    (
+        length.parse().unwrap(),
+        amount.parse().unwrap(),
+        marker_length,
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::decompress_sequence;
+
+    #[test]
+    fn example_a1() {
+        assert_eq!(decompress_sequence("ADVENT"), "ADVENT");
+    }
+
+    #[test]
+    fn example_a2() {
+        assert_eq!(decompress_sequence("A(1x5)BC"), "ABBBBBC");
+    }
+
+    #[test]
+    fn example_a3() {
+        assert_eq!(decompress_sequence("(3x3)XYZ"), "XYZXYZXYZ");
+    }
+
+    #[test]
+    fn example_a4() {
+        assert_eq!(decompress_sequence("A(2x2)BCD(2x2)EFG"), "ABCBCDEFEFG");
+    }
+
+    #[test]
+    fn example_a5() {
+        assert_eq!(decompress_sequence("(6x1)(1x3)A"), "(1x3)A");
+    }
+
+    #[test]
+    fn example_a6() {
+        assert_eq!(decompress_sequence("X(8x2)(3x3)ABCY"), "X(3x3)ABC(3x3)ABCY");
+    }
+}