Added Solution for 2021 day 04

2021/day04_giant_squid/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "day04_giant_squid"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

2021/day04_giant_squid/challenge.txt

@@ -0,0 +1,90 @@
+You're already almost 1.5km (almost a mile) below the surface of the ocean, already so deep that you can't see any sunlight. What you *can* see, however, is a giant squid that has attached itself to the outside of your submarine.
+
+Maybe it wants to play [bingo](https://en.wikipedia.org/wiki/Bingo_(American_version))?
+
+Bingo is played on a set of boards each consisting of a 5x5 grid of numbers. Numbers are chosen at random, and the chosen number is *marked* on all boards on which it appears. (Numbers may not appear on all boards.) If all numbers in any row or any column of a board are marked, that board *wins*. (Diagonals don't count.)
+
+The submarine has a *bingo subsystem* to help passengers (currently, you and the giant squid) pass the time. It automatically generates a random order in which to draw numbers and a random set of boards (your puzzle input). For example:
+
+```
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
+
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
+
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7
+
+```
+
+After the first five numbers are drawn (`7`, `4`, `9`, `5`, and `11`), there are no winners, but the boards are marked as follows (shown here adjacent to each other to save space):
+
+```
+22 13 17 11  0         3 15  0  2 22        14 21 17 24  4
+ 8  2 23  4 24         9 18 13 17  5        10 16 15  9 19
+21  9 14 16  7        19  8  7 25 23        18  8 23 26 20
+ 6 10  3 18  5        20 11 10 24  4        22 11 13  6  5
+ 1 12 20 15 19        14 21 16 12  6         2  0 12  3  7
+
+```
+
+After the next six numbers are drawn (`17`, `23`, `2`, `0`, `14`, and `21`), there are still no winners:
+
+```
+22 13 17 11  0         3 15  0  2 22        14 21 17 24  4
+ 8  2 23  4 24         9 18 13 17  5        10 16 15  9 19
+21  9 14 16  7        19  8  7 25 23        18  8 23 26 20
+ 6 10  3 18  5        20 11 10 24  4        22 11 13  6  5
+ 1 12 20 15 19        14 21 16 12  6         2  0 12  3  7
+
+```
+
+Finally, `24` is drawn:
+
+```
+22 13 17 11  0         3 15  0  2 22        14 21 17 24  4
+ 8  2 23  4 24         9 18 13 17  5        10 16 15  9 19
+21  9 14 16  7        19  8  7 25 23        18  8 23 26 20
+ 6 10  3 18  5        20 11 10 24  4        22 11 13  6  5
+ 1 12 20 15 19        14 21 16 12  6         2  0 12  3  7
+
+```
+
+At this point, the third board *wins* because it has at least one complete row or column of marked numbers (in this case, the entire top row is marked: `*14 21 17 24 4*`).
+
+The *score* of the winning board can now be calculated. Start by finding the *sum of all unmarked numbers* on that board; in this case, the sum is `188`. Then, multiply that sum by *the number that was just called* when the board won, `24`, to get the final score, `188 * 24 = *4512*`.
+
+To guarantee victory against the giant squid, figure out which board will win first. *What will your final score be if you choose that board?*
+
+Your puzzle answer was `45031`.
+
+\--- Part Two ---
+----------
+
+On the other hand, it might be wise to try a different strategy: let the giant squid win.
+
+You aren't sure how many bingo boards a giant squid could play at once, so rather than waste time counting its arms, the safe thing to do is to *figure out which board will win last* and choose that one. That way, no matter which boards it picks, it will win for sure.
+
+In the above example, the second board is the last to win, which happens after `13` is eventually called and its middle column is completely marked. If you were to keep playing until this point, the second board would have a sum of unmarked numbers equal to `148` for a final score of `148 * 13 = *1924*`.
+
+Figure out which board will win last. *Once it wins, what would its final score be?*
+
+Your puzzle answer was `2568`.
+
+Both parts of this puzzle are complete! They provide two gold stars: \*\*
+
+At this point, you should [return to your Advent calendar](/2021) and try another puzzle.
+
+If you still want to see it, you can [get your puzzle input](4/input).

2021/day04_giant_squid/src/lib.rs

@@ -0,0 +1,119 @@
+use core::fmt::Display;
+use std::num::ParseIntError;
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum ParseError {
+    InputMalformed(String),
+    ParseIntError(std::num::ParseIntError),
+    LineMalformed(String),
+}
+
+impl From<ParseIntError> for ParseError {
+    fn from(value: ParseIntError) -> Self {
+        Self::ParseIntError(value)
+    }
+}
+
+impl Display for ParseError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::InputMalformed(v) => write!(f, "Input is malformed: {v}"),
+            Self::ParseIntError(e) => write!(f, "Unable to parse into integer: {e}"),
+            Self::LineMalformed(v) => write!(f, "Line is malformed: {v}"),
+        }
+    }
+}
+
+struct BingoBoard {
+    rows: [[usize; 5]; 5],
+    ticked: Vec<(usize, usize)>,
+    done: bool,
+}
+
+impl TryFrom<&str> for BingoBoard {
+    type Error = ParseError;
+
+    fn try_from(value: &str) -> Result<Self, Self::Error> {
+        let mut rows = [[0; 5]; 5];
+        let lines: Vec<_> = value.lines().collect();
+        if lines.len() != 5 {
+            return Err(Self::Error::InputMalformed(value.to_string()));
+        }
+        for (y, line) in lines.iter().enumerate() {
+            let numbers: Vec<_> = line.split_whitespace().collect();
+            if numbers.len() != 5 {
+                return Err(Self::Error::LineMalformed(line.to_string()));
+            }
+            for (x, n) in numbers.iter().enumerate() {
+                rows[y][x] = n.parse()?;
+            }
+        }
+
+        Ok(Self{ rows, ticked: Vec::new(), done: false })
+    }
+}
+
+impl BingoBoard {
+    fn tick(&mut self, number: usize) -> Option<usize> {
+        if !self.done {
+            if let Some((x, y)) = self.rows.iter().enumerate().find(|(_y, row)| row.contains(&number)).map(|(y, row)| (row.iter().position(|n| *n == number).unwrap(), y)) {
+                self.ticked.push((x, y));
+                if self.ticked.iter().filter(|(col, _row)| *col == x).count() == 5 ||
+                    self.ticked.iter().filter(|(_col, row)| *row == y).count() == 5 {
+                        self.done = true;
+                        return Some(number);
+                    }
+            }
+        }
+        None
+    }
+
+    fn sum_unmarked(&self) -> usize {
+        self.rows.iter().enumerate().map(|(y, row)| row.iter().enumerate().filter(|(x, _n)| !self.ticked.contains(&(*x, y))).map(|(_x, n)| n).sum::<usize>()).sum()
+    }
+}
+
+pub fn run(input: &str) -> Result<(usize, usize), ParseError> {
+    let items: Vec<_> = input.split("\n\n").collect();
+    let numbers: Vec<_> = items[0].split(',').map(|i| i.parse::<usize>()).collect::<Result<Vec<_>, _>>()?;
+    let mut boards: Vec<_> = items[1..].iter().map(|b| BingoBoard::try_from(*b)).collect::<Result<Vec<_>, _>>()?;
+    let mut todo = boards.len();
+    let mut first = 0;
+    let mut second = 0;
+    'outer: for number in numbers {
+        for board in boards.iter_mut() {
+            if let Some(last) = board.tick(number) {
+                if first == 0 {
+                    first = last * board.sum_unmarked();
+                } else if todo == 1 {
+                    second = last * board.sum_unmarked();
+                    break 'outer;
+                }
+                todo -= 1;
+            }
+        }
+    };
+    Ok((first, second))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs::read_to_string;
+
+    fn read_file(name: &str) -> String {
+        read_to_string(name).expect(&format!("Unable to read file: {name}")[..]).trim().to_string()
+    }
+
+    #[test]
+    fn test_sample() {
+        let sample_input = read_file("tests/sample_input");
+        assert_eq!(run(&sample_input), Ok((4512, 1924)));
+    }
+
+    #[test]
+    fn test_challenge() {
+        let challenge_input = read_file("tests/challenge_input");
+        assert_eq!(run(&challenge_input), Ok((45031, 2568)));
+    }
+}

2021/day04_giant_squid/tests/challenge_input

@@ -0,0 +1,601 @@
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+
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+
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+
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2021/day04_giant_squid/tests/sample_input

@@ -0,0 +1,19 @@
+7,4,9,5,11,17,23,2,0,14,21,24,10,16,13,6,15,25,12,22,18,20,8,19,3,26,1
+
+22 13 17 11  0
+ 8  2 23  4 24
+21  9 14 16  7
+ 6 10  3 18  5
+ 1 12 20 15 19
+
+ 3 15  0  2 22
+ 9 18 13 17  5
+19  8  7 25 23
+20 11 10 24  4
+14 21 16 12  6
+
+14 21 17 24  4
+10 16 15  9 19
+18  8 23 26 20
+22 11 13  6  5
+ 2  0 12  3  7