feat: add day4

solutions/04.sql

@@ -0,0 +1,90 @@
+create or replace table day04_data as
+select
+  row_number() over() as row,
+  column0
+from
+  read_csv(
+    'inputs/04/input.txt',
+    header = false
+  );
+create or replace table day04_test as
+select
+  row_number() over() as row,
+  column0
+from
+  read_csv(
+    'inputs/04/test.txt',
+    header = false
+  );
+
+create or replace table day04_clean as
+select
+  row,
+  idx + 1 as col
+from
+  day04_data
+cross join unnest(range(length(column0))) as t(idx)
+where substr(column0, idx + 1, 1) = '@';
+
+create or replace table day04_neighbors as
+select
+  c.row * 1000 + c.col as node,
+  a.row * 1000 + a.col as neighbor
+from day04_clean as c
+left join day04_clean as a
+  on a.row between (c.row - 1) and (c.row + 1)
+  and a.col between (c.col - 1) and (c.col + 1)
+;
+
+with neighbors_count as (
+  select node, count(1) as nb_neighbors
+  from day04_neighbors
+  group by node
+)
+select count_if(nb_neighbors <= 4) as part1
+from neighbors_count
+;
+
+with recursive seq as (
+  with agg as (
+    select
+        node,
+        count(1) neighbors
+    from day04_neighbors
+    group by node
+    having neighbors > 4
+  )
+  select
+    node,
+    s.neighbor,
+    (select count(distinct node) from agg) as remaining,
+    0 as step
+  from day04_neighbors as s
+  inner join agg as a1 using (node)
+  inner join agg as a2 on a2.node = s.neighbor
+
+  union all
+
+  (
+    with agg2 as (
+      select node, step, count(distinct neighbor) as neighbors
+      from seq
+      group by node, step
+      having step = (select max(step) from seq)
+      and neighbors > 4
+    )
+    select
+      s.node,
+      s.neighbor,
+      (select count(distinct node) from agg2) as remaining,
+      s.step + 1 as step 
+    from seq s
+    inner join agg2 as a1 using(node)
+    inner join agg2 as a2 on a2.node = s.neighbor
+    where (
+      select count(distinct node) from agg2) < (select min(remaining) from seq
+    )
+  )
+)
+select (select count(distinct node) from day04_neighbors) - (select min(remaining) from seq) as part2;
+