From 4a731b3d7f5aadb8d4681f43a104791d4dfc912e Mon Sep 17 00:00:00 2001
From: Ishan Jain <contact@ishanjain.me>
Date: Sat, 4 Dec 2021 12:55:54 +0530
Subject: [PATCH] Added Day 4 Part 2

---
 inputs/day4.sample.txt |   3 +-
 src/main.rs            | 116 ++++++++++++++++++++++-------------------
 2 files changed, 62 insertions(+), 57 deletions(-)

diff --git a/inputs/day4.sample.txt b/inputs/day4.sample.txt
index f06791d..49d17bc 100644
--- a/inputs/day4.sample.txt
+++ b/inputs/day4.sample.txt
@@ -16,5 +16,4 @@
 10 16 15  9 19
 18  8 23 26 20
 22 11 13  6  5
- 2  0 12  3  7
-
+ 2  0 12  3  7
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index 95389b6..75a9ee3 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -6,17 +6,62 @@ const INPUTS: [&'static str; 2] = [
     include_str!("../inputs/day4.txt"),
 ];
 
-#[derive(Copy, Clone, Debug)]
+const WINNING_COMBINATIONS: [[(usize, usize); 5]; 5] = [
+    // Row wins
+    [(0, 0), (0, 1), (0, 2), (0, 3), (0, 4)],
+    [(1, 0), (1, 1), (1, 2), (1, 3), (1, 4)],
+    [(2, 0), (2, 1), (2, 2), (2, 3), (2, 4)],
+    [(3, 0), (3, 1), (3, 2), (3, 3), (3, 4)],
+    [(4, 0), (4, 1), (4, 2), (4, 3), (4, 4)],
+];
+
+#[derive(Copy, Clone, Debug, Hash, Eq, PartialEq)]
 enum BoardEntry {
     Entry(u64),
-    CalledEntry(u64),
+    Called(u64),
     Null,
 }
 
-#[derive(Copy, Clone, Debug)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
 struct Board {
     board: [[BoardEntry; 5]; 5],
     sum: u64,
+    won: bool,
+}
+
+impl Board {
+    fn mark_draw(&mut self, draw: u64) {
+        for row in self.board.iter_mut() {
+            for val in row.iter_mut() {
+                if let BoardEntry::Entry(v) = val {
+                    if *v == draw {
+                        self.sum -= *v;
+                        *val = BoardEntry::Called(*v);
+                    }
+                }
+            }
+        }
+    }
+
+    fn is_winner(&self) -> bool {
+        for set in WINNING_COMBINATIONS.iter() {
+            let col_match = set
+                .iter()
+                .map(|&(x, y)| self.board[y][x])
+                .all(|entry| matches!(entry, BoardEntry::Called(_)));
+
+            let row_match = set
+                .iter()
+                .map(|&(x, y)| self.board[x][y])
+                .all(|entry| matches!(entry, BoardEntry::Called(_)));
+
+            if row_match || col_match {
+                return true;
+            }
+        }
+
+        false
+    }
 }
 
 fn cmds(input: &'static str) -> (Vec<u64>, Vec<Board>) {
@@ -35,6 +80,7 @@ fn cmds(input: &'static str) -> (Vec<u64>, Vec<Board>) {
         let mut bblock = Board {
             board: [[BoardEntry::Null; 5]; 5],
             sum: 0,
+            won: false,
         };
 
         for (i, line) in block.split('\n').enumerate() {
@@ -52,63 +98,23 @@ fn cmds(input: &'static str) -> (Vec<u64>, Vec<Board>) {
 }
 
 fn solution((draws, mut boards): (Vec<u64>, Vec<Board>)) -> u64 {
+    let mut answer = 0;
+
     for draw in draws {
-        // Mark boards
-
-        mark_entry(&mut boards, draw);
-
-        if let Some(board) = check_winner(&boards) {
-            return board.sum * draw;
-        }
-    }
-
-    0
-}
-
-fn check_winner(boards: &[Board]) -> Option<&Board> {
-    for board in boards {
-        let grid = board.board;
-
-        for i in 0..5 {
-            if grid[i]
-                .iter()
-                .all(|x| matches!(x, BoardEntry::CalledEntry(_)))
-            {
-                return Some(board);
+        for board in boards.iter_mut() {
+            if board.won {
+                continue;
             }
-        }
+            board.mark_draw(draw);
 
-        for j in 0..5 {
-            let mut all_called = true;
-            for i in 0..5 {
-                if !matches!(grid[i][j], BoardEntry::CalledEntry(_)) {
-                    all_called = false;
-                    break;
-                }
-            }
-
-            if all_called {
-                return Some(board);
+            if board.is_winner() {
+                answer = board.sum * draw;
+                board.won = true;
             }
         }
     }
 
-    None
-}
-
-fn mark_entry(boards: &mut [Board], called: u64) {
-    for board in boards {
-        for row in board.board.iter_mut() {
-            for col in row.iter_mut() {
-                if let BoardEntry::Entry(val) = col {
-                    if *val == called {
-                        board.sum -= *val;
-                        *col = BoardEntry::CalledEntry(*val);
-                    }
-                }
-            }
-        }
-    }
+    answer
 }
 
 fn main() {
@@ -121,9 +127,9 @@ fn main() {
 
 #[bench]
 fn solution_bench(b: &mut test::Bencher) {
+    let input = cmds(INPUTS[1]);
     b.iter(|| {
-        let input = cmds(INPUTS[1]);
-        let result = solution(input);
+        let result = solution(input.clone());
         test::black_box(result);
     })
 }