day 5 part 2

src/day5/mod.rs

@@ -1 +1,2 @@
 pub mod part1;
+pub mod part2;

src/day5/part2.rs

@@ -0,0 +1,53 @@
+use std::{fs, ops::RangeInclusive};
+
+#[allow(dead_code)]
+pub fn solve() {
+    let file = fs::read_to_string("src/day5/input.txt").expect("You didn't provide input.txt.");
+
+    let mut original_ranges = Vec::<RangeInclusive<usize>>::new();
+    let mut fresh_products_ranges = Vec::<RangeInclusive<usize>>::new();
+
+    // Initialize the ranges
+    for line in file.lines() {
+        if line.is_empty() {
+            break;
+        }
+
+        let mut parts = line.split("-");
+        let start = parts.next().unwrap().parse::<usize>().unwrap();
+        let end = parts.next().unwrap().parse::<usize>().unwrap();
+        original_ranges.push(start..=end);
+    }
+
+    // Sort them by start for easier merge in next step
+    original_ranges.sort_by_key(|range| *range.start());
+
+    // merge overlappers
+    for range in original_ranges {
+        if fresh_products_ranges.is_empty() {
+            fresh_products_ranges.push(range);
+            continue;
+        }
+
+        let last_idx = fresh_products_ranges.len() - 1;
+        let last_range = &fresh_products_ranges[last_idx];
+
+        if *range.start() <= *last_range.end() + 1 {
+            let new_end = *last_range.end().max(range.end());
+            let new_start = *last_range.start();
+
+            fresh_products_ranges[last_idx] = new_start..=new_end;
+        } else {
+            fresh_products_ranges.push(range);
+        }
+    }
+
+    let fresh_products_count = {
+        let mut cnt = 0;
+        for range in &fresh_products_ranges {
+            cnt += range.end() - range.start() + 1;
+        }
+        cnt
+    };
+    println!("Fresh products: {:?}", fresh_products_count);
+}

src/main.rs

@@ -5,5 +5,5 @@ mod day4;
 mod day5;
 
 fn main() {
-    day5::solve();
+    day5::part2::solve();
 }