WITH MUTUALLY RECURSIVE
lines(r INT, line TEXT) AS (
SELECT r, regexp_split_to_array(input, '\n')[r] as block
FROM input, generate_series(1, array_length(regexp_split_to_array(input, '\n'), 1)) r
),
cells(r INT, c INT, symbol TEXT) AS (
SELECT r, c, substring(line, c, 1)
FROM lines, generate_series(1, length(line)) c
),
northward(r INT, c INT, symbol TEXT) AS (
SELECT * FROM northward
-- Anyone on the move does so
UNION ALL SELECT r - 1, c, 'O' FROM north_move
EXCEPT ALL SELECT r - 1, c, '.' FROM north_move
UNION ALL SELECT r, c, '.' FROM north_move
EXCEPT ALL SELECT r, c, 'O' FROM north_move
-- Initial state is cells, but not refreshed each round.
UNION ALL SELECT * FROM cells
EXCEPT ALL SELECT * FROM cells_delay
),
-- Each 'O' with a '.' to the north will move.
north_move(r INT, c INT) AS (
SELECT n1.r, n1.c
FROM northward n1, northward n2
WHERE n1.symbol = 'O'
AND n1.r = n2.r + 1
AND n1.c = n2.c
AND n2.symbol = '.'
),
part1(part1 BIGINT) AS (
SELECT SUM(1 + (SELECT MAX(r) FROM lines) - r)
FROM northward
WHERE symbol = 'O'
),
output (r INT, line TEXT) AS (
SELECT r, string_agg(symbol, ' ' ORDER BY c)
FROM northward
GROUP BY r
),
cells_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM cells )
SELECT * FROM part1; WITH MUTUALLY RECURSIVE (RETURN AT RECURSION LIMIT 142)
lines(r INT, line TEXT) AS (
SELECT r, regexp_split_to_array(input, '\n')[r] as block
FROM input, generate_series(1, array_length(regexp_split_to_array(input, '\n'), 1)) r
),
cells(r INT, c INT, symbol TEXT) AS (
SELECT r, c, substring(line, c, 1)
FROM lines, generate_series(1, length(line)) c
),
-- Where should we start each iteration from?
-- From `east`, once it exits, but initially `cells`.
round(r INT, c INT, symbol TEXT) AS (
SELECT * FROM east
UNION ALL SELECT * FROM cells
EXCEPT ALL SELECT * FROM cells_delay
),
north(r INT, c INT, symbol TEXT) AS (
WITH MUTUALLY RECURSIVE
start(r INT, c INT, symbol TEXT) AS (
SELECT * FROM round
),
northward(r INT, c INT, symbol TEXT) AS (
SELECT * FROM northward
-- Anyone on the move does so
UNION ALL SELECT r - 1, c, 'O' FROM north_move
EXCEPT ALL SELECT r - 1, c, '.' FROM north_move
UNION ALL SELECT r, c, '.' FROM north_move
EXCEPT ALL SELECT r, c, 'O' FROM north_move
-- Second time around, the above cancels and `east` is non-empty.
UNION ALL SELECT * FROM start
EXCEPT ALL SELECT * FROM start_delay
),
-- Each 'O' with a '.' in front of them will move.
north_move(r INT, c INT) AS (
SELECT n1.r, n1.c
FROM northward n1, northward n2
WHERE n1.symbol = 'O'
AND n1.r = n2.r + 1
AND n1.c = n2.c
AND n2.symbol = '.'
),
start_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM start )
SELECT * FROM northward
),
west(r INT, c INT, symbol TEXT) AS (
WITH MUTUALLY RECURSIVE
start(r INT, c INT, symbol TEXT) AS (
SELECT * FROM north
),
westward(r INT, c INT, symbol TEXT) AS (
SELECT * FROM westward
-- Anyone on the move does so
UNION ALL SELECT r, c - 1, 'O' FROM west_move
EXCEPT ALL SELECT r, c - 1, '.' FROM west_move
UNION ALL SELECT r, c, '.' FROM west_move
EXCEPT ALL SELECT r, c, 'O' FROM west_move
-- Initial state is cells, but not refreshed each round.
UNION ALL SELECT * FROM start
EXCEPT ALL SELECT * FROM start_delay
),
-- Each 'O' with a '.' in front of them will move.
west_move(r INT, c INT) AS (
SELECT w1.r, w1.c
FROM westward w1, westward w2
WHERE w1.symbol = 'O'
AND w1.r = w2.r
AND w1.c = w2.c + 1
AND w2.symbol = '.'
),
start_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM start )
SELECT * FROM westward
),
south(r INT, c INT, symbol TEXT) AS (
WITH MUTUALLY RECURSIVE
start(r INT, c INT, symbol TEXT) AS (
SELECT * FROM west
),
southward(r INT, c INT, symbol TEXT) AS (
SELECT * FROM southward
-- Anyone on the move does so
UNION ALL SELECT r + 1, c, 'O' FROM south_move
EXCEPT ALL SELECT r + 1, c, '.' FROM south_move
UNION ALL SELECT r, c, '.' FROM south_move
EXCEPT ALL SELECT r, c, 'O' FROM south_move
-- Initial state is cells, but not refreshed each round.
UNION ALL SELECT * FROM start
EXCEPT ALL SELECT * FROM start_delay
),
-- Each 'O' with a '.' in front of them will move.
south_move(r INT, c INT) AS (
SELECT s1.r, s1.c
FROM southward s1, southward s2
WHERE s1.symbol = 'O'
AND s1.r = s2.r - 1
AND s1.c = s2.c
AND s2.symbol = '.'
),
start_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM start )
SELECT * FROM southward
),
east(r INT, c INT, symbol TEXT) AS (
WITH MUTUALLY RECURSIVE
start(r INT, c INT, symbol TEXT) AS (
SELECT * FROM south
),
eastward(r INT, c INT, symbol TEXT) AS (
SELECT * FROM eastward
-- Anyone on the move does so
UNION ALL SELECT r, c + 1, 'O' FROM east_move
EXCEPT ALL SELECT r, c + 1, '.' FROM east_move
UNION ALL SELECT r, c, '.' FROM east_move
EXCEPT ALL SELECT r, c, 'O' FROM east_move
-- Initial state is cells, but not refreshed each round.
UNION ALL SELECT * FROM start
EXCEPT ALL SELECT * FROM start_delay
),
-- Each 'O' with a '.' in front of them will move.
east_move(r INT, c INT) AS (
SELECT e1.r, e1.c
FROM eastward e1, eastward e2
WHERE e1.symbol = 'O'
AND e1.r = e2.r
AND e1.c = e2.c - 1
AND e2.symbol = '.'
),
start_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM start )
SELECT * FROM eastward
),
output (r INT, line TEXT) AS (
SELECT r, string_agg(symbol, ' ' ORDER BY c)
FROM round
GROUP BY r
),
transitions(source TEXT, target TEXT) AS (
SELECT
(SELECT string_agg(symbol, '' ORDER BY r, c) FROM round),
(SELECT string_agg(symbol, '' ORDER BY r, c) FROM east)
UNION ALL
SELECT * FROM transitions
),
part2(part2 BIGINT) AS (
SELECT SUM(1 + (SELECT MAX(r) FROM lines) - r)
FROM east
WHERE symbol = 'O'
),
cells_delay(r INT, c INT, symbol TEXT) AS ( SELECT * FROM cells )
-- SELECT count, COUNT(*)
-- FROM (
-- SELECT source, target, COUNT(*) count
-- FROM transitions
-- GROUP BY source, target)
-- GROUP BY count;
-- SELECT * FROM output ORDER BY r;
SELECT * FROM part2;Day 14 was brought to you by: @frankmcsherry