day 4 solutions

learnt how rust does macros.

day_4/src/main.rs

@@ -1,3 +1,43 @@
-fn main() {
+use std::fs::read_to_string;
-    println!("Hello, world!");
+
+const PATH: &str = "src/input";
+
+macro_rules! val_in_range {
+    ($test:expr, $l:expr, $u:expr) => {
+        $test >= $l && $test <= $u
+    };
+}
+
+// [l1,u1] inside of [l2,u2]
+macro_rules! range_in_range {
+    ($l1:expr, $u1:expr, $l2:expr, $u2:expr) => {
+        $l1 <= $l2 && $u1 >= $u2
+    };
+}
+
+fn main() {
+    let binding = read_to_string(PATH).expect("Error reading file");
+    let data = binding.split_ascii_whitespace().into_iter();
+    let mut overlapping_ranges_pt1: u32 = 0;
+    let mut overlapping_ranges_pt2: u32 = 0;
+    for pair in data {
+        let ranges: Vec<u32> = pair
+            .split(&['-', ','])
+            .map(|x| x.parse().unwrap())
+            .collect();
+
+        overlapping_ranges_pt2 += (val_in_range!(ranges[0], ranges[2], ranges[3])
+            || val_in_range!(ranges[1], ranges[2], ranges[3])
+            || val_in_range!(ranges[2], ranges[0], ranges[1])
+            || val_in_range!(ranges[3], ranges[0], ranges[1]))
+            as u32;
+
+        overlapping_ranges_pt1 += (range_in_range!(ranges[0], ranges[1], ranges[2], ranges[3])
+            || range_in_range!(ranges[2], ranges[3], ranges[0], ranges[1]))
+            as u32
+    }
+    println!(
+        "PART 1 {}\nPART 2 {}",
+        overlapping_ranges_pt1, overlapping_ranges_pt2
+    );
 }