small tweak in day11

src/day11.rs

@@ -39,7 +39,7 @@ fn sum_paths_mat(start_idx: usize, end_idx: usize, adj_matrix: &Vec<Vec<usize>>)
     loop {
         paths = paths + step[(start_idx, end_idx)] as u64;
         step = &adj_mat * step;
-        if step.sum() < 0.1 {
+        if step.row(start_idx).sum() < 0.1 {
             break;
         }
     }