day16

1 files changed, 87 insertions, 0 deletions

diff --git a/src/day16pt2.rs b/src/day16pt2.rs
new file mode 100644
index 0000000..9e2f094
--- /dev/null
+++ b/src/day16pt2.rs
@@ -0,0 +1,87 @@
+use std::collections::HashMap;
+
+fn bfs(
+    input: &Vec<Vec<char>>,
+    was: &mut Vec<Vec<bool>>,
+    x: i32,
+    y: i32,
+    dx: i32,
+    dy: i32,
+    comb: &mut HashMap<(i32, i32, i32, i32), i32>,
+) {
+    if x < 0
+        || x >= input[0].len() as i32
+        || y < 0
+        || y >= input.len() as i32
+        || comb.contains_key(&(x, y, dx, dy))
+    {
+        return;
+    }
+
+    let c = input[y as usize][x as usize];
+    was[y as usize][x as usize] = true;
+    comb.insert((x, y, dx, dy), 1);
+
+    if c == '/' {
+        bfs(input, was, x - dy, y - dx, -dy, -dx, comb);
+    } else if c == '\\' {
+        bfs(input, was, x + dy, y + dx, dy, dx, comb);
+    } else if c == '|' {
+        if dy != 0 {
+            bfs(input, was, x + dx, y + dy, dx, dy, comb);
+        } else {
+            bfs(input, was, x, y - 1, 0, -1, comb);
+            bfs(input, was, x, y + 1, 0, 1, comb);
+        }
+    } else if c == '-' {
+        if dx != 0 {
+            bfs(input, was, x + dx, y + dy, dx, dy, comb);
+        } else {
+            bfs(input, was, x - 1, y, -1, 0, comb);
+            bfs(input, was, x + 1, y, 1, 0, comb);
+        }
+    } else if c == '.' {
+        bfs(input, was, x + dx, y + dy, dx, dy, comb);
+    }
+}
+
+fn try_comb(input: &Vec<Vec<char>>, x: i32, y: i32, dx: i32, dy: i32) -> usize {
+    let mut was = vec![vec![false; input[0].len()]; input.len()];
+    let mut comb = HashMap::new();
+
+    bfs(&input, &mut was, x, y, dx, dy, &mut comb);
+
+    let mut sum = 0;
+    for i in was {
+        sum += i.iter().filter(|&n| *n == true).count();
+    }
+
+    return sum;
+}
+
+pub fn main() {
+    let txt = std::fs::read_to_string("./input/day16.txt").unwrap();
+    let input = txt
+        .lines()
+        .map(|s| s.chars().collect::<Vec<char>>())
+        .collect::<Vec<Vec<char>>>();
+
+    let mut m = 0;
+    for i in 0..input.len() {
+        m = usize::max(m, try_comb(&input, 0, i as i32, 1, 0));
+        m = usize::max(
+            m,
+            try_comb(&input, (input[0].len() - 1) as i32, i as i32, -1, 0),
+        );
+    }
+
+    for i in 0..input[0].len() {
+        m = usize::max(m, try_comb(&input, i as i32, 0, 0, 1));
+        m = usize::max(
+            m,
+            try_comb(&input, i as i32, (input.len() - 1) as i32, 0, -1),
+        );
+    }
+
+    println!("{}", m);
+}