1 files changed, 46 insertions, 0 deletions
diff --git a/2017/src/bin/day_13.rs b/2017/src/bin/day_13.rs
new file mode 100644
index 0000000..e85b541
--- /dev/null
+++ b/2017/src/bin/day_13.rs
@@ -0,0 +1,46 @@
+extern crate advent_of_code_2017;
+use advent_of_code_2017::*;
+
+use std::collections::HashMap;
+
+fn main() {
+    let args = AdventArgs::init();
+
+    let input: HashMap<u32, u32> = args.input.iter().map(|line| {
+        let mut split_line = line.split(": ");
+        (split_line.next().unwrap().parse().unwrap(), split_line.next().unwrap().parse().unwrap())
+    }).collect();
+
+    if args.part == 1 {
+        let severity = calculate_severity(&input, 0, &args);
+        println!("Severity: {}", severity);
+    } else {
+        let optimal_delay = (0u32..).find(|&delay| calculate_severity(&input, delay, &args) == 0).unwrap();
+        println!("Wait {} picoseconds", optimal_delay);
+    }
+}
+
+fn calculate_severity(input: &HashMap<u32, u32>, delay: u32, args: &AdventArgs) -> u32 {
+    let mut severity = 0;
+    let max_depth = input.keys().max().cloned().unwrap();
+        
+    for depth in 0..max_depth+1 {
+        severity += match input.get(&depth) {
+            Some(range) => {
+                let position = (depth + delay) % (2*range-2);
+
+                if position == 0 {
+                    if args.part == 1 {
+                        range * depth
+                    } else {
+                        range * depth + 1
+                    }
+                } else {
+                    0
+                }
+            },
+            None => 0
+        };
+    }
+    severity
+}