From 5399e43d48eda82586b05d1e25d01c7171bf9eef Mon Sep 17 00:00:00 2001
From: Justin Worthe <justin@worthe-it.co.za>
Date: Wed, 13 Dec 2017 07:55:33 +0200
Subject: Day 13: Navigating the firewall

---
 inputs/day_13.txt         | 43 +++++++++++++++++++++++++++++++++++++++++++
 inputs/day_13_example.txt |  5 +++++
 src/bin/day_13.rs         | 46 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 94 insertions(+)
 create mode 100644 inputs/day_13.txt
 create mode 100644 inputs/day_13_example.txt
 create mode 100644 src/bin/day_13.rs

diff --git a/inputs/day_13.txt b/inputs/day_13.txt
new file mode 100644
index 0000000..87bfdb7
--- /dev/null
+++ b/inputs/day_13.txt
@@ -0,0 +1,43 @@
+0: 3
+1: 2
+2: 4
+4: 4
+6: 5
+8: 6
+10: 6
+12: 6
+14: 6
+16: 8
+18: 8
+20: 8
+22: 8
+24: 10
+26: 8
+28: 8
+30: 12
+32: 14
+34: 12
+36: 10
+38: 12
+40: 12
+42: 9
+44: 12
+46: 12
+48: 12
+50: 12
+52: 14
+54: 14
+56: 14
+58: 12
+60: 14
+62: 14
+64: 12
+66: 14
+70: 14
+72: 14
+74: 14
+76: 14
+80: 18
+88: 20
+90: 14
+98: 17
diff --git a/inputs/day_13_example.txt b/inputs/day_13_example.txt
new file mode 100644
index 0000000..0de4bec
--- /dev/null
+++ b/inputs/day_13_example.txt
@@ -0,0 +1,5 @@
+0: 3
+1: 2
+4: 4
+6: 4
+
diff --git a/src/bin/day_13.rs b/src/bin/day_13.rs
new file mode 100644
index 0000000..e85b541
--- /dev/null
+++ b/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
+}
-- 
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