1 files changed, 62 insertions, 0 deletions
diff --git a/11/src/part-2.rs b/11/src/part-2.rs
new file mode 100644
index 0000000..3bdb50e
--- /dev/null
+++ b/11/src/part-2.rs
@@ -0,0 +1,62 @@
+mod tensor;
+
+use std::io::{BufRead};
+
+pub type Matrix<T> = tensor::Tensor<T, 2>;
+pub type Index = tensor::Index<2>;
+
+
+pub fn main() {
+    let stdin = std::io::stdin();
+    let handle = stdin.lock();
+
+    let mut energy: Matrix<usize> = {
+        let mut tmp: Vec<usize> = Vec::new();
+        let mut m: usize = 0;
+        for l in handle.lines() {
+            let line = l.unwrap();
+            tmp.extend(line.chars().map(|c| c.to_digit(10).unwrap() as usize));
+            m += 1;
+        }
+        let n = tmp.len()/m;
+        Matrix::new_from([m, n], tmp)
+    };
+    let m = energy.shape()[0];
+    let n = energy.shape()[1];
+
+    let mut can_flash: Matrix<bool> = Matrix::new(energy.shape().clone(), true);
+    let mut to_increase: Vec<Index> = Vec::new();
+    for s in 0.. {
+        can_flash.fill(true);
+        to_increase.clear();
+        for i in 0..m {
+            for j in 0..n {
+                to_increase.push([i, j]);
+            }
+        }
+
+        while let Some(idx) = to_increase.pop() {
+            if can_flash[idx] {
+                energy[idx] += 1;
+                if energy[idx] > 9 {
+                    let neighbors: [Index; 8] = [[idx[0]                 , idx[1].wrapping_sub(1)], [idx[0]  , idx[1]+1],
+                                                 [idx[0].wrapping_sub(1) , idx[1]                ], [idx[0]+1, idx[1]  ],
+                                                 [idx[0].wrapping_sub(1) , idx[1].wrapping_sub(1)], [idx[0]+1, idx[1]+1],
+                                                 [idx[0].wrapping_sub(1) , idx[1]+1              ], [idx[0]+1, idx[1].wrapping_sub(1)] ];
+                    energy[idx] = 0;
+                    can_flash[idx] = false;
+                    for neighbor in (& neighbors).into_iter().filter(|neighbor| energy.in_bounds(neighbor)) {
+                        to_increase.push(*neighbor);
+                    }
+                }
+            }
+        }
+
+        let e = energy[[0,0]];
+        if energy.data().into_iter().all(|& x| x == e) {
+            println!("Synchronized after step {} (so answer is step {})", s, s+1);
+            break;
+        }
+    }
+
+}