From bf568133656374c7ce68fb0d0b5537e36e4efbff Mon Sep 17 00:00:00 2001
From: nekineki <nekineki@nekineki.net>
Date: Fri, 13 Dec 2024 06:52:07 +0100
Subject: day13

---
 2024/day13.rs | 134 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 134 insertions(+)
 create mode 100644 2024/day13.rs

(limited to '2024/day13.rs')

diff --git a/2024/day13.rs b/2024/day13.rs
new file mode 100644
index 0000000..dd18923
--- /dev/null
+++ b/2024/day13.rs
@@ -0,0 +1,134 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+#![allow(unused_mut)]
+use std::env;
+use std::fs::File;
+use std::io::Read;
+
+#[derive(Debug, PartialEq, Clone)]
+struct Machine {
+    ax: i128,
+    ay: i128,
+    bx: i128,
+    by: i128,
+    px: i128,
+    py: i128,
+}
+
+fn solve(m: &Machine) -> Option<i128> {
+    let mut min_price = None;
+
+    for a in 0..100 {
+        for b in 0..100 {
+            let x = a * m.ax + b * m.bx;
+            let y = a * m.ay + b * m.by;
+            if x == m.px && y == m.py {
+                let price = a * 3 + b * 1;
+                if min_price == None || price < min_price.unwrap() {
+                    min_price = Some(price);
+                }
+            }
+        }
+    }
+
+    min_price
+}
+
+fn solve2(m: &Machine) -> Option<i128> {
+    let n1 = m.px * m.ay - m.py * m.ax;
+    let n2 = m.bx * m.ay - m.by * m.ax;
+
+    if n1 % n2 != 0 {
+        return None;
+    }
+    let b = n1 / n2;
+
+    let n1 = m.px - b * m.bx;
+    let n2 = m.ax;
+    if n1 % n2 != 0 {
+        return None;
+    }
+    let a = n1 / n2;
+
+    Some(a * 3 + b)
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let filename = if args.len() == 1 {
+        "in/".to_owned() + args[0].split('/').last().unwrap() + ".pzl"
+    } else {
+        args[1].clone()
+    };
+    let mut f = File::open(filename).expect("cannot open file");
+    let mut content = String::new();
+    f.read_to_string(&mut content).expect("cannot read file");
+    let para = content.trim_end().split("\n\n");
+
+    let mut mvec: Vec<Machine> = Vec::new();
+    for lines in para {
+        let mut m: Machine = Machine {
+            ax: 0,
+            ay: 0,
+            bx: 0,
+            by: 0,
+            px: 0,
+            py: 0,
+        };
+
+        let (s, rest) = lines.split_once("X+").unwrap();
+        let (s, rest) = rest.split_once(",").unwrap();
+        m.ax = s.parse().unwrap();
+
+        let (s, rest) = rest.split_once("Y+").unwrap();
+        let (s, rest) = rest.split_once("\n").unwrap();
+        m.ay = s.parse().unwrap();
+
+        let (s, rest) = rest.split_once("X+").unwrap();
+        let (s, rest) = rest.split_once(",").unwrap();
+        m.bx = s.parse().unwrap();
+
+        let (s, rest) = rest.split_once("Y+").unwrap();
+        let (s, rest) = rest.split_once("\n").unwrap();
+        m.by = s.parse().unwrap();
+
+        let (s, rest) = rest.split_once("X=").unwrap();
+        let (s, rest) = rest.split_once(",").unwrap();
+        m.px = s.parse().unwrap();
+
+        let (s, rest) = rest.split_once("Y=").unwrap();
+        m.py = rest.parse().unwrap();
+
+        mvec.push(m);
+    }
+
+    let mut res1 = 0;
+    let mut res2 = 0;
+
+    for m in &mvec {
+        let p1 = solve(m);
+        if let Some(val) = p1 {
+            //println!("{}", val);
+            res1 += val;
+        }
+        let m2: Machine = Machine {
+            ax: m.ax,
+            ay: m.ay,
+            bx: m.bx,
+            by: m.by,
+            px: m.px + 10000000000000,
+            py: m.py + 10000000000000,
+        };
+
+        let p2 = solve2(&m2);
+        if let Some(val) = p2 {
+            //println!("{}", val);
+            res2 += val;
+        }
+    }
+
+    println!("res1: {}", res1);
+    println!("res2: {}", res2);
+    assert_eq!(res1, 29187);
+    assert_eq!(res2, 99968222587852);
+}
-- 
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