Add day 23

Author: LinAGKar

Day23_input.txt

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+916438275

day23a/Cargo.toml

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+[package]
+name = "day23a"
+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]

day23a/src/main.rs

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+use std::io::Read;
+
+fn main() {
+    let mut input = String::new();
+    std::io::stdin().read_to_string(&mut input).unwrap();
+
+    let mut cups = u64::from_str_radix(input.trim(), 16).unwrap();
+    let cup_count = input.trim().len();
+    let pick_up_mask = (0..cup_count - 4).fold(0, |acc, n| acc | (0xF << n * 4));
+    let keep_masks: Vec<_> = (0..cup_count).map(|i| {
+        (0..i).fold(0, |acc, j| acc | 0xF << j * 4)
+    }).collect();
+
+    for _ in 0..100 {
+        let current_cup = cups >> (cup_count - 1) * 4;
+        let removed_cups = cups >> (cup_count - 4) * 4 & 0xFFF;
+        cups = current_cup << (cup_count - 4) * 4 | cups & pick_up_mask;
+        let destination = (current_cup as usize - 1..current_cup as usize + cup_count - 1).rev().find_map(|cup| {
+            let cup = cup % cup_count + 1;
+            if let Some(pos) = (0..cup_count).find(|pos| cups >> pos * 4 & 0xF == cup as u64) {
+                Some(pos)
+            } else {
+                None
+            }
+        }).unwrap();
+        cups = cups & keep_masks[destination] |
+               cups >> destination * 4 << (destination + 3) * 4 |
+               removed_cups << destination * 4;
+        cups = (cups & keep_masks[cup_count - 1]) << 4 | cups >> (cup_count - 1) * 4;
+    }
+
+    while cups & 0xF != 1 {
+        cups = (cups & 0xF) << (cup_count - 1) * 4 | cups >> 4;
+    }
+
+    println!("{:X}", cups >> 4);
+}

day23a/testinput

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+389125467

day23b/Cargo.toml

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+[package]
+name = "day23b"
+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]

day23b/src/main.rs

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+use std::io::Read;
+
+fn main() {
+    let mut input = String::new();
+    std::io::stdin().read_to_string(&mut input).unwrap();
+    // Changing this to usize works, but more than doubles the runtime
+    type ItemType = u32;
+    const FULL_CUP_COUNT: ItemType = 1000000;
+
+    let initial_cups: Vec<_> = input.trim().chars().map(|digit| digit.to_digit(10).unwrap() as ItemType).collect();
+    // Lookup table for the next cup after each cup
+    let mut cups: Vec<_> = (0..FULL_CUP_COUNT + 1).map(|x| x + 1).collect();
+    let mut current_cup = initial_cups[0];
+    *cups.last_mut().unwrap() = current_cup;
+    for (i, &cup) in initial_cups.iter().enumerate() {
+        cups[cup as usize] = if i == initial_cups.len() - 1 {
+            if FULL_CUP_COUNT as usize > initial_cups.len() {
+                (initial_cups.len() + 1) as ItemType
+            } else {
+                current_cup
+            }
+        } else {
+            initial_cups[i + 1]
+        }
+    }
+
+    for _ in 0..10000000 {
+        let first_removed = cups[current_cup as usize];
+        let last_removed = (0..2).fold(first_removed, |acc, _| cups[acc as usize]);
+        cups[current_cup as usize] = cups[last_removed as usize];
+
+        let destination = (current_cup - 1..current_cup + FULL_CUP_COUNT - 1).rev().find_map(|i| {
+            let cup = i % FULL_CUP_COUNT + 1;
+            if (0..3).try_fold(first_removed, |acc, _| {
+                if cup == acc {
+                    Err(())
+                } else {
+                    Ok(cups[acc as usize])
+                }
+            }).is_ok() {
+                Some(cup)
+            } else {
+                None
+            }
+        }).unwrap();
+        cups[last_removed as usize] = cups[destination as usize];
+        cups[destination as usize] = first_removed;
+        current_cup = cups[current_cup as usize];
+    }
+
+    // For part 1
+    // (0..FULL_CUP_COUNT - 1).fold(1, |acc, _| {
+    //     let next = cups[acc as usize];
+    //     print!("{}", next);
+    //     next
+    // });
+    // println!("");
+
+    println!("{}", (0..2).fold((1, 1), |(cup, product), _| {
+        let next = cups[cup as usize];
+        (next, product * next as u64)
+    }).1);
+}