day4

2 files changed, 30 insertions, 0 deletions

diff --git a/src/day4.rs b/src/day4.rs
new file mode 100644
index 0000000..46b9077
--- /dev/null
+++ b/src/day4.rs
@@ -0,0 +1,27 @@
+pub fn run(input: String) {
+    let count_overlaps = input.lines().map(|line| {
+        let (r1s, r2s) = line.split_once(",").expect("couldn't split on comma");
+        let (r1starts,r1ends) = r1s.split_once("-").expect("r1s no delimiter -");
+        let (r2starts,r2ends) = r2s.split_once("-").expect("r2s no delimiter -");
+        let r1start: u32 = r1starts.parse().expect("r1starts not a u32");
+        let r1end: u32 = r1ends.parse().expect("r1ends not a u32");
+        let r2start: u32 = r2starts.parse().expect("r2starts not a u32");
+        let r2end: u32 = r2ends.parse().expect("r2ends not a u32");
+        // fully contained (i.e. r1 is fully inside r2 or vice versa)
+        //let b1in2 = r1start >= r2start && r1end <= r2end;
+        //let b2in1 = r2start >= r1start && r2end <= r1end;
+        //return b1in2 || b2in1;
+
+        // partially contained (i.e. at least one end of r1 is contained in r2, or vice versa)
+        let e1 = r1start >= r2start && r1start <= r2end;
+        let e2 = r1end >= r2start && r1end <= r2end;
+        let e3 = r2start >= r1start && r2start <= r1end;
+        let e4 = r2end >= r1start && r2end <= r1end;
+        let res = e1 || e2 || e3 || e4;
+        //println!("{}: {}", line, res);
+        res
+    }) 
+        .filter(|x| {*x})
+        .count();
+    println!("Day 4: {}", count_overlaps);
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 79c5970..c257999 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4,8 +4,11 @@ mod day1;
 mod day2;
 mod day3;
 
+mod day4;
+
 fn main() {
     day1::run(fs::read_to_string("input/day1.txt").expect("Failed to read input file!"));
     day2::run(fs::read_to_string("input/day2.txt").expect("Failed to read input file!"));
     day3::run(fs::read_to_string("input/day3.txt").expect("Failed to read input file!"));
+    day4::run(fs::read_to_string("input/day4.txt").expect("Failed to read input file!"));
 }