Added AOC 2020 day 03 - 14

www/statics/aoc/2020/13_solution.rs

@@ -0,0 +1,94 @@
+use crate::common::AdventOfCodeDay;
+
+pub struct Day13 {
+    input_time: u32,
+    input_bus: Vec<Option<u32>>,
+}
+
+impl Day13 {
+    pub fn new() -> Self {
+        let input_bytes = include_bytes!("../res/13_input.txt");
+        let input_str = String::from_utf8_lossy(input_bytes);
+        
+        let t = input_str.lines().next().unwrap().parse::<u32>().unwrap();
+
+        let b = input_str.lines().skip(1).next().unwrap().split(',').map(|p| p.parse::<u32>().ok()).collect::<Vec<Option<u32>>>();
+
+        Self {
+            input_time: t,
+            input_bus: b,
+        }
+    }
+
+    fn ext_euclid(a: i128, b: i128) -> (i128, i128, i128) {
+        if a == 0 {
+            return (b, 0, 1);
+        }
+
+        let (gcd, x1, y1) = Day13::ext_euclid(b%a, a);
+
+        let x = y1 - (b/a) * x1;
+        let y = x1;
+        
+        return (gcd, x, y);
+    }
+}
+
+impl AdventOfCodeDay for Day13 {
+
+    fn task_1(&self) -> String {
+
+        let mut b = self.input_bus
+                .iter()
+                .flat_map(|p| p.iter())
+                .map(|p| *p)
+                .collect::<Vec<u32>>();
+        
+        b.sort_by(|a,b| (self.input_time % b).cmp(&(self.input_time % a)));
+
+        verboseln!("{}", self.input_time);
+        verboseln!("{:?}", b);
+        verboseln!("{:?}", b.iter().map(|p| p - self.input_time % p).collect::<Vec<u32>>());
+
+        return (b[0] * (b[0] - self.input_time % b[0])).to_string();
+    }
+
+    fn task_2(&self) -> String  {
+
+        // https://en.wikipedia.org/wiki/Chinese_remainder_theorem
+        // https://mathepedia.de/Chinesischer_Restsatz.html
+
+        let formulas = self.input_bus
+                           .iter()
+                           .enumerate()
+                           .filter(|(_,p)| p.is_some())
+                           .map(|(i,p)| (i, p.unwrap()))
+                           .map(|(i,p)| ((-(i as i128) % p as i128 + p as i128) as i128 % p as i128, p as i128))
+                           .collect::<Vec<(i128, i128)>>();
+
+        if is_verbose!() {
+            verboseln!();
+            //for (i,b) in &formulas { verboseln!("t = {: <3} | {: <3}", i, b); }
+            for (i,b) in &formulas { verboseln!("t % {: <3} = {: <3}", b, i); }
+            verboseln!();
+        }
+
+        let mut m = 1;
+        for (_, mi) in &formulas { m *= mi; }
+
+
+        let mut x = 0;
+        for (ai, mi) in &formulas {
+            let (gcd, ri, si) = Day13::ext_euclid(*mi as i128, m / *mi as i128);
+            let ei = si * (m / *mi as i128);
+
+            x += ai * ei;
+            verbosedbg!(m, m / *mi as i128, ai, mi, gcd, ri, si, ei, x);
+            verboseln!();
+        }
+
+        x = ((x % m) + m) % m;
+        
+        return x.to_string() //TODO
+    }
+}