Added day 13

inputs/day13.txt

@@ -0,0 +1,2 @@
+1000655
+17,x,x,x,x,x,x,x,x,x,x,37,x,x,x,x,x,571,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,13,x,x,x,x,23,x,x,x,x,x,29,x,401,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,19

inputs/test.txt

@@ -1,5 +1,2 @@
-F10
-N3
-F7
-R90
-F11
+939
+7,13,x,x,59,x,31,19

src/bin/day13.rs

@@ -0,0 +1,32 @@
+use itertools::Itertools;
+use std::error::Error;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::vec::Vec;
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let file = File::open("inputs/day13.txt")?;
+    let mut lines = io::BufReader::new(file).lines().map(|l| l.unwrap());
+
+    let depature_time: u32 = lines.nth(0).unwrap().parse().unwrap();
+    let buses: Vec<u32> = lines
+        .nth(0)
+        .unwrap()
+        .split(',')
+        .filter_map(|b| b.parse().ok())
+        .collect();
+
+    let times: Vec<(u32, u32)> = buses
+        .iter()
+        .map(|b| (*b, b - (depature_time % b)))
+        .collect();
+
+    let best_time = times
+        .iter()
+        .fold(times[0], |a, b| if a.1 < b.1 { a } else { *b });
+
+    println!("Line: {}, Wait Time: {}", best_time.0, best_time.1);
+    println!("Answer: {}", best_time.0 * best_time.1);
+
+    Ok(())
+}

src/bin/day13_part2.rs

@@ -0,0 +1,51 @@
+use itertools::Itertools;
+use std::error::Error;
+use std::fs::File;
+use std::io::{self, BufRead};
+use std::vec::Vec;
+
+fn next_depature(t: u64, b: u64) -> u64 {
+    if t % b == 0 {
+        0
+    } else {
+        b - (t % b)
+    }
+}
+
+fn print_rests(t: u64, buses: &Vec<Option<u64>>) {
+    for i in 0..buses.len() {
+        if let Some(bus) = buses[i] {
+            println!("{} : {} {}", bus, i, t % bus);
+        }
+    }
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let file = File::open("inputs/day13.txt")?;
+    let mut lines = io::BufReader::new(file).lines().map(|l| l.unwrap());
+
+    let buses: Vec<Option<u64>> = lines
+        .nth(1)
+        .unwrap()
+        .split(',')
+        .map(|b| b.parse().ok())
+        .collect();
+
+    let mut step = buses[0].unwrap();
+    let mut t: u64 = 0;
+    for i in 1..buses.len() {
+        if let Some(bus) = buses[i] {
+            loop {
+                t = t + step;
+                if (t + i as u64) % bus == 0 {
+                    step = step * bus;
+                    break;
+                }
+            }
+        }
+    }
+
+    println!("{}", t);
+
+    Ok(())
+}