day 04 part 2

days/day04/src/main.rs

@@ -10,5 +10,5 @@ fn main() {
     println!("Result: {}", part1::part1(&structured_input));
 
     println!("Part Two");
-    println!("Result: {}", part2::part2());
+    println!("Result: {}", part2::part2(&structured_input));
 }

days/day04/src/parse.rs

@@ -7,11 +7,12 @@ use nom::{
     IResult,
 };
 
-#[derive(Debug, PartialEq, Eq,)]
+#[derive(Debug, PartialEq, Eq, Clone)]
 pub struct Card {
     pub id: usize,
     pub winning_numbers: BTreeSet<u8>,
     pub numbers: BTreeSet<u8>,
+    pub multiplier: usize,
 }
 
 impl Card {
@@ -36,15 +37,13 @@ impl Card {
                 id: id as usize,
                 winning_numbers,
                 numbers,
+                multiplier: 1,
             },
         ))
     }
 
-    pub fn winning_number_matches(&self) -> BTreeSet<u8> {
+    pub fn num_matches(&self) -> usize {
-        self.numbers
+        self.numbers.intersection(&self.winning_numbers).count()
-            .intersection(&self.winning_numbers)
-            .cloned()
-            .collect()
     }
 }
 
@@ -73,32 +72,38 @@ mod tests {
                 Card {
                     id: 1,
                     winning_numbers: collection! {17, 41, 48, 83, 86},
-                    numbers: collection! {6, 9, 17, 31, 48, 53, 83, 86}
+                    numbers: collection! {6, 9, 17, 31, 48, 53, 83, 86},
+                    multiplier: 1,
                 },
                 Card {
                     id: 2,
                     winning_numbers: collection! {13, 16, 20, 32, 61},
-                    numbers: collection! {17, 19, 24, 30, 32, 61, 68, 82}
+                    numbers: collection! {17, 19, 24, 30, 32, 61, 68, 82},
+                    multiplier: 1,
                 },
                 Card {
                     id: 3,
                     winning_numbers: collection! {1, 21, 44, 53, 59},
-                    numbers: collection! {1, 14, 16, 21, 63, 69, 72, 82}
+                    numbers: collection! {1, 14, 16, 21, 63, 69, 72, 82},
+                    multiplier: 1,
                 },
                 Card {
                     id: 4,
                     winning_numbers: collection! {41, 69, 73, 84, 92},
-                    numbers: collection! {5, 51, 54, 58, 59, 76, 83, 84}
+                    numbers: collection! {5, 51, 54, 58, 59, 76, 83, 84},
+                    multiplier: 1,
                 },
                 Card {
                     id: 5,
                     winning_numbers: collection! {26, 28, 32, 83, 87},
-                    numbers: collection! {12, 22, 30, 36, 70, 82, 88, 93}
+                    numbers: collection! {12, 22, 30, 36, 70, 82, 88, 93},
+                    multiplier: 1,
                 },
                 Card {
                     id: 6,
                     winning_numbers: collection! {13 , 18, 31, 56, 72},
-                    numbers: collection! {10, 11, 23, 35, 36, 67, 74, 77}
+                    numbers: collection! {10, 11, 23, 35, 36, 67, 74, 77},
+                    multiplier: 1,
                 }
             ]
         );
@@ -115,6 +120,7 @@ mod tests {
                     id: 1,
                     winning_numbers: collection! {41, 48, 83, 86, 17},
                     numbers: collection! {83, 86, 6, 31, 17, 9, 48, 53},
+                    multiplier: 1,
                 }
             )
         )

days/day04/src/part1.rs

@@ -4,7 +4,7 @@ pub fn part1(input: &[Card]) -> usize {
     input
         .iter()
         .map(|c| {
-            let len = c.winning_number_matches().len();
+            let len = c.num_matches();
             if len >= 1 {
                 2_usize.pow((len - 1).try_into().unwrap())
             } else {
@@ -27,31 +27,37 @@ mod tests {
                 id: 1,
                 winning_numbers: collection! {17, 41, 48, 83, 86},
                 numbers: collection! {6, 9, 17, 31, 48, 53, 83, 86},
+                multiplier: 1,
             },
             Card {
                 id: 2,
                 winning_numbers: collection! {13, 16, 20, 32, 61},
                 numbers: collection! {17, 19, 24, 30, 32, 61, 68, 82},
+                multiplier: 1,
             },
             Card {
                 id: 3,
                 winning_numbers: collection! {1, 21, 44, 53, 59},
                 numbers: collection! {1, 14, 16, 21, 63, 69, 72, 82},
+                multiplier: 1,
             },
             Card {
                 id: 4,
                 winning_numbers: collection! {41, 69, 73, 84, 92},
                 numbers: collection! {5, 51, 54, 58, 59, 76, 83, 84},
+                multiplier: 1,
             },
             Card {
                 id: 5,
                 winning_numbers: collection! {26, 28, 32, 83, 87},
                 numbers: collection! {12, 22, 30, 36, 70, 82, 88, 93},
+                multiplier: 1,
             },
             Card {
                 id: 6,
                 winning_numbers: collection! {13 , 18, 31, 56, 72},
                 numbers: collection! {10, 11, 23, 35, 36, 67, 74, 77},
+                multiplier: 1,
             },
         ];
         assert_eq!(part1(&input), 13);

days/day04/src/part2.rs

@@ -1,15 +1,65 @@
 use crate::parse::*;
 
-pub fn part2() -> usize {
+pub fn part2(input: &[Card]) -> usize {
-    unimplemented!()
+    let mut stack: Vec<Card> = input.to_vec();
+    for i in 0..stack.len() {
+        let matches = stack[i].num_matches();
+        if matches >= 1 {
+            //+1 because we want 3 matches to give the num 1,2,3
+            for advance in 1..(matches+1){
+                stack[i+advance].multiplier+=stack[i].multiplier
+            }
+        }
+    }
+    stack.iter().map(|c| c.multiplier).sum()
 }
 
 #[cfg(test)]
 mod tests {
+    use collection_literals::collection;
+
     use super::*;
 
     #[test]
     fn test_part2() {
-        assert_eq!(0, 0);
+        let input = vec![
+            Card {
+                id: 1,
+                winning_numbers: collection! {17, 41, 48, 83, 86},
+                numbers: collection! {6, 9, 17, 31, 48, 53, 83, 86},
+                multiplier: 1,
+            },
+            Card {
+                id: 2,
+                winning_numbers: collection! {13, 16, 20, 32, 61},
+                numbers: collection! {17, 19, 24, 30, 32, 61, 68, 82},
+                multiplier: 1,
+            },
+            Card {
+                id: 3,
+                winning_numbers: collection! {1, 21, 44, 53, 59},
+                numbers: collection! {1, 14, 16, 21, 63, 69, 72, 82},
+                multiplier: 1,
+            },
+            Card {
+                id: 4,
+                winning_numbers: collection! {41, 69, 73, 84, 92},
+                numbers: collection! {5, 51, 54, 58, 59, 76, 83, 84},
+                multiplier: 1,
+            },
+            Card {
+                id: 5,
+                winning_numbers: collection! {26, 28, 32, 83, 87},
+                numbers: collection! {12, 22, 30, 36, 70, 82, 88, 93},
+                multiplier: 1,
+            },
+            Card {
+                id: 6,
+                winning_numbers: collection! {13 , 18, 31, 56, 72},
+                numbers: collection! {10, 11, 23, 35, 36, 67, 74, 77},
+                multiplier: 1,
+            },
+        ];
+        assert_eq!(part2(&input), 30);
     }
 }