add day 4 (it was easy)

src/bin/04.rs

@@ -0,0 +1,56 @@
+use regex::Regex;
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let linere = Regex::new(r"(\d+)-(\d+),(\d+)-(\d+)").unwrap();
+    let mut result = 0;
+    for l in input.lines() {
+        let caps = linere.captures(l).unwrap();
+        let s1 = &caps[1].parse::<i32>().unwrap();
+        let e1 = &caps[2].parse::<i32>().unwrap();
+        let s2 = &caps[3].parse::<i32>().unwrap();
+        let e2 = &caps[4].parse::<i32>().unwrap();
+        if (s2 >= s1 && e2 <= e1) || (s1 >= s2 && e1 <= e2) {
+            result += 1;
+        }
+    }
+    Some(result)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let linere = Regex::new(r"(\d+)-(\d+),(\d+)-(\d+)").unwrap();
+    let mut result = 0;
+    for l in input.lines() {
+        let caps = linere.captures(l).unwrap();
+        let s1 = &caps[1].parse::<i32>().unwrap();
+        let e1 = &caps[2].parse::<i32>().unwrap();
+        let s2 = &caps[3].parse::<i32>().unwrap();
+        let e2 = &caps[4].parse::<i32>().unwrap();
+        if !((s2 > e1 && e2 > e1) || (s1 > e2 && e1 > e2))  {
+            result += 1;
+        }
+    }
+    Some(result)
+}
+
+fn main() {
+    let input = &advent_of_code::read_file("inputs", 4);
+    advent_of_code::solve!(1, part_one, input);
+    advent_of_code::solve!(2, part_two, input);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let input = advent_of_code::read_file("examples", 4);
+        assert_eq!(part_one(&input), Some(2));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let input = advent_of_code::read_file("examples", 4);
+        assert_eq!(part_two(&input), Some(4));
+    }
+}

src/examples/04.txt

@@ -0,0 +1,6 @@
+2-4,6-8
+2-3,4-5
+5-7,7-9
+2-8,3-7
+6-6,4-6
+2-6,4-8