Add day 13

Author: LinAGKar

Day13_input.txt

@@ -0,0 +1,2 @@
+1005526
+37,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,41,x,x,x,x,x,x,x,x,x,587,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,13,19,x,x,x,23,x,x,x,x,x,29,x,733,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,x,17

day13a/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "day13a"
+version = "0.1.0"
+authors = ["Linus Kardell <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day13a/src/main.rs

@@ -0,0 +1,16 @@
+use std::io;
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_line(&mut input).unwrap();
+    let curr_time: i32 = input.trim().parse().unwrap();
+
+    input.clear();
+    io::stdin().read_line(&mut input).unwrap();
+    let (id, remain) = input.trim().split(",").filter(|&x| x != "x").map(|x| {
+        let period: i32 = x.parse().unwrap();
+        (period, (-curr_time).rem_euclid(period))
+    }).min_by_key(|&(_, remain)| remain).unwrap();
+
+    println!("{}", id * remain);
+}

day13b/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "day13b"
+version = "0.1.0"
+authors = ["Linus Kardell <[email protected]>"]
+edition = "2018"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

day13b/src/main.rs

@@ -0,0 +1,36 @@
+use std::io;
+
+fn gcd(a: u64, b: u64) -> u64 {
+    if b == 0 {
+        a
+    } else {
+        gcd(b, a % b)
+    }
+}
+
+fn lcm(a: u64, b: u64) -> u64 {
+    a * b / gcd(a, b)
+}
+
+fn main() {
+    let mut input = String::new();
+    io::stdin().read_line(&mut input).unwrap();
+
+    input.clear();
+    io::stdin().read_line(&mut input).unwrap();
+
+    let (_, offset) = input
+        .trim()
+        .split(",")
+        .enumerate()
+        .filter(|&(_, x)| x != "x")
+        .fold((1, 0), |(old_period, offset), (n, x)| {
+            let new_period = x.parse().unwrap();
+            (
+                lcm(old_period, new_period),
+                (0..).map(|y| old_period * y + offset).find(|y| (y + n as u64) % new_period == 0).unwrap(),
+            )
+        });
+
+    println!("{}", offset);
+}