Day 4 part 2 brute force

2023/rust/src/day4.rs

@@ -9,7 +9,10 @@ use nom::{
     sequence::tuple,
     IResult,
 };
-use std::{collections::HashSet, iter::FromIterator};
+use std::{
+    collections::{HashMap, HashSet},
+    iter::FromIterator,
+};
 
 use crate::prelude::*;
 
@@ -25,11 +28,14 @@ struct Card {
 }
 
 impl Card {
+    fn num_winning(&self) -> usize {
+        self.has.iter().filter(|n| self.winning.contains(n)).count() as usize
+    }
+
     fn points(&self) -> usize {
-        let num_winning = self.has.iter().filter(|n| self.winning.contains(n)).count() as u32;
-        println!("{self:?} num_winning -> {num_winning}");
-        if num_winning >= 1 {
-            2_u64.pow(num_winning - 1) as usize
+        let n = self.num_winning();
+        if n >= 1 {
+            2_u64.pow((n - 1) as u32) as usize
         } else {
             0
         }
@@ -60,7 +66,27 @@ impl AoCSolution for Day4 {
     }
 
     fn part2(input: Self::Input) -> Self::Solution {
-        0
+        let mut result = 0;
+        let mut copies: HashMap<usize, usize> = HashMap::new();
+        input.lines().for_each(|s| {
+            let card = card(s).unwrap().1;
+            println!("{}, cur result: {}", card.id, result);
+            let mut num_copies = 1;
+            if let Some(extra_copies) = copies.get(&card.id) {
+                num_copies += extra_copies;
+            }
+            for _ in 1..=num_copies {
+                for i in card.id..=(card.id + card.num_winning()) {
+                    if let Some(n) = copies.get_mut(&i) {
+                        *n += 1;
+                    } else {
+                        copies.insert(i, 1);
+                    }
+                }
+            }
+            result += num_copies
+        });
+        result
     }
 }
 
@@ -78,6 +104,6 @@ Card 5: 87 83 26 28 32 | 88 30 70 12 93 22 82 36
 Card 6: 31 18 13 56 72 | 74 77 10 23 35 67 36 11"#;
         println!("input:\n{input}");
         assert_eq!(Day4::part1(input.into()), 13);
-        assert_eq!(Day4::part2(input.into()), 0);
+        assert_eq!(Day4::part2(input.into()), 30);
     }
 }