Solution for 2022/day04-part2

2022/day04-part2/src/main.rs

@@ -0,0 +1,46 @@
+use std::collections::HashSet;
+
+fn main() {
+    // Use command line arguments to specify the input filename.
+    let args: Vec<String> = std::env::args().collect();
+    if args.len() < 2 {
+        panic!("Usage: ./main <input-file>\nNo input file provided. Exiting.");
+    }
+
+    // Next, read the contents of the input file into a string for easier processing.
+    let input = std::fs::read_to_string(&args[1]).expect("Error opening file");
+    // Line-by-line processing is easiest.
+    let input = input.lines();
+
+    // --- TASK BEGIN ---
+    let mut count = 0;
+
+    for line in input {
+        // Turn "1-2,3-6" into ["1-2", "3-6"].
+        let ranges = line.split(',').collect::<Vec<_>>();
+        // Turn ["1-2", "3-6"] into [["1", "2"], ["3", "6"]]
+        let ranges = ranges
+            .iter()
+            .map(|x| x.split('-').collect::<Vec<_>>())
+            .collect::<Vec<_>>();
+        // Turn [["1", "2"], ["3", "6"]] into [1..=2, 3..=6]
+        let ranges = ranges
+            .iter()
+            .map(|x| (x[0].parse::<i32>().unwrap())..=(x[1].parse::<i32>().unwrap()))
+            .collect::<Vec<_>>();
+        // Now turn the ranges into HashSets containing the respective integers. Essentially:
+        // Turn [1..=2, 3..=6] into [{1,2}, {3,4,5,6}]
+        let sets = ranges
+            .into_iter()
+            .map(|x| x.collect::<HashSet<_>>())
+            .collect::<Vec<_>>();
+
+        // Check if the two sets are disjoint.
+        // If there's at least one overlapping element, add it to the count.
+        if !sets[0].is_disjoint(&sets[1]) {
+            count += 1;
+        }
+    }
+
+    println!("Count: {}", count);
+}