WITH MUTUALLY RECURSIVE
blocks(block1 TEXT, block2 TEXT) AS (
SELECT
regexp_split_to_array(input, '\n\n')[1] block1,
regexp_split_to_array(input, '\n\n')[2] block2
FROM input
),
states(state TEXT, trans TEXT) AS (
SELECT
regexp_split_to_array(line, '\{')[1] state,
trim('}' FROM regexp_split_to_array(line, '\{')[2]) trans
FROM (SELECT regexp_split_to_table(block1, '\n') line FROM blocks)
),
steps(state TEXT, priority INT, rule TEXT) AS (
SELECT
state,
priority,
regexp_split_to_array(trans, ',')[priority]
FROM states, generate_series(1, array_length(regexp_split_to_array(trans, ','), 1)) priority
),
starts(x INT, m INT, a INT, s INT) AS (
SELECT
substring(regexp_split_to_array(trimmed, ',')[1], 3)::INT,
substring(regexp_split_to_array(trimmed, ',')[2], 3)::INT,
substring(regexp_split_to_array(trimmed, ',')[3], 3)::INT,
substring(regexp_split_to_array(trimmed, ',')[4], 3)::INT
FROM (SELECT trim('\{' FROM trim('\}' FROM regexp_split_to_table(block2, '\n'))) trimmed FROM blocks)
),
--
rules(state TEXT, priority INT, field TEXT, cmp TEXT, val INT, next TEXT) AS (
SELECT
state,
priority,
CASE WHEN substring(rule, 2, 1) = '<' OR substring(rule, 2, 1) = '>'
THEN substring(rule, 1, 1)
ELSE 'x'
END,
CASE WHEN substring(rule, 2, 1) = '<' OR substring(rule, 2, 1) = '>'
THEN substring(rule, 2, 1)
ELSE '>'
END,
CASE WHEN substring(rule, 2, 1) = '<' OR substring(rule, 2, 1) = '>'
THEN regexp_split_to_array(substring(rule, 3), ':')[1]::INT
ELSE '0'
END,
CASE WHEN substring(rule, 2, 1) = '<' OR substring(rule, 2, 1) = '>'
THEN regexp_split_to_array(substring(rule, 3), ':')[2]
ELSE rule
END
FROM steps
),
-- PART 1: iterate folks forward from `in`
movement(state TEXT, x INT, m INT, a INT, s INT) AS (
SELECT 'in' state, * FROM starts
UNION ALL
SELECT next, x, m, a, s
FROM (
SELECT DISTINCT ON (state, x, m, a, s) state, x, m, a, s, priority, next
FROM (
SELECT movement.*, rules.next, rules.priority
FROM movement, rules
WHERE movement.state = rules.state
AND CASE WHEN rules.cmp = '<'
THEN CASE WHEN rules.field = 'x' THEN x < val
WHEN rules.field = 'm' THEN m < val
WHEN rules.field = 'a' THEN a < val
WHEN rules.field = 's' THEN s < val
ELSE false
END
WHEN rules.cmp = '>'
THEN CASE WHEN rules.field = 'x' THEN x > val
WHEN rules.field = 'm' THEN m > val
WHEN rules.field = 'a' THEN a > val
WHEN rules.field = 's' THEN s > val
ELSE false
END
ELSE false
END
)
ORDER BY state, x, m, a, s, priority
)
),
part1(part1 BIGINT) AS (
SELECT SUM(x + m + a + s)
FROM movement
WHERE state = 'A'
),
-- PART 2: just find all the bounding regions and label them 'A' or 'R'.
region(state TEXT, priority INT, xl INT, xu INT, ml INT, mu INT, al INT, au INT, sl INT, su INT) AS (
SELECT 'in', 1, 1, 4000, 1, 4000, 1, 4000, 1, 4000
-- Could satisfy the rule, and transition to the next state ..
UNION ALL
SELECT
next,
1,
CASE WHEN rules.field = 'x' AND rules.cmp = '>' THEN GREATEST(val+1, xl) ELSE xl END,
CASE WHEN rules.field = 'x' AND rules.cmp = '<' THEN LEAST(val-1, xu) ELSE xu END,
CASE WHEN rules.field = 'm' AND rules.cmp = '>' THEN GREATEST(val+1, ml) ELSE ml END,
CASE WHEN rules.field = 'm' AND rules.cmp = '<' THEN LEAST(val-1, mu) ELSE mu END,
CASE WHEN rules.field = 'a' AND rules.cmp = '>' THEN GREATEST(val+1, al) ELSE al END,
CASE WHEN rules.field = 'a' AND rules.cmp = '<' THEN LEAST(val-1, au) ELSE au END,
CASE WHEN rules.field = 's' AND rules.cmp = '>' THEN GREATEST(val+1, sl) ELSE sl END,
CASE WHEN rules.field = 's' AND rules.cmp = '<' THEN LEAST(val-1, su) ELSE su END
FROM region, rules
WHERE region.state = rules.state
AND region.priority = rules.priority
-- .. or could fail the rule, and advance to the next priority.
UNION ALL
SELECT
region.state,
region.priority + 1,
CASE WHEN rules.field = 'x' AND rules.cmp = '<' THEN GREATEST(val, xl) ELSE xl END,
CASE WHEN rules.field = 'x' AND rules.cmp = '>' THEN LEAST(val, xu) ELSE xu END,
CASE WHEN rules.field = 'm' AND rules.cmp = '<' THEN GREATEST(val, ml) ELSE ml END,
CASE WHEN rules.field = 'm' AND rules.cmp = '>' THEN LEAST(val, mu) ELSE mu END,
CASE WHEN rules.field = 'a' AND rules.cmp = '<' THEN GREATEST(val, al) ELSE al END,
CASE WHEN rules.field = 'a' AND rules.cmp = '>' THEN LEAST(val, au) ELSE au END,
CASE WHEN rules.field = 's' AND rules.cmp = '<' THEN GREATEST(val, sl) ELSE sl END,
CASE WHEN rules.field = 's' AND rules.cmp = '>' THEN LEAST(val, su) ELSE su END
FROM region, rules
WHERE region.state = rules.state
AND region.priority = rules.priority
),
part2(part2 NUMERIC) AS (
SELECT SUM((1 + xu - xl)::BIGINT * (1 + mu - ml)::BIGINT * (1 + au - al)::BIGINT * (1 + su - sl)::BIGINT)
FROM region
WHERE state = 'A'
),
potato(x INT) AS (SELECT 1)
SELECT * FROM part1, part2;Day 19 was brought to you by: @frankmcsherry