Solutions to day 20

2016/day-20/src/main.rs

@@ -0,0 +1,41 @@
+use std::env;
+use std::io::prelude::*;
+use std::io::BufReader;
+use std::fs::File;
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let f = File::open(&args[1]).expect("Could not open file");
+    let reader = BufReader::new(f);
+
+    let mut ranges = Vec::new();
+
+    // Assumption: No overlapping ranges
+    for line in reader.lines() {
+        let contents = line.unwrap();
+        let parts: Vec<&str> = contents.split("-").collect();
+        let lo: u32 = parts[0].parse().unwrap();
+        let hi: u32 = parts[1].parse().unwrap();
+
+        ranges.push((lo, hi));
+    }
+
+    ranges.sort();
+
+    let mut min_blocked = 0;
+    let mut unblocked = 0;
+    for (start, end) in ranges {
+        if start > min_blocked && start - min_blocked > 1 {
+            if unblocked == 0 {
+                println!("First non-blocked at {}", min_blocked + 1);
+            }
+            unblocked += start - min_blocked - 1;
+        }
+
+        if end > min_blocked {
+            min_blocked = end;
+        }
+    }
+
+    println!("{} allowed ips", unblocked);
+}