2118. Build the Equation (Hard).sql

-- Table Name for Test-Case 1: terms_2118
-- Table Name for Test-Case 2: terms_2118_tc_2

WITH terms AS (
SELECT power,ABS(factor) AS factor,
 (CASE WHEN factor <0 THEN '-' ELSE '+' END) AS sign,
 (CASE WHEN power =1 THEN CONCAT(ABS(factor),'X')
 WHEN power =0 THEN ABS(factor)::TEXT
 ELSE CONCAT(ABS(factor),'X^',power)
 END) AS term
FROM terms_2118
)
SELECT CONCAT(STRING_AGG(CONCAT(sign,term),''ORDER BY power DESC),'=0') AS equation
FROM terms;

-- Solution of the follow-up question (Table : terms_2118_tc_3)

WITH grouped_terms AS (
SELECT power,SUM(factor) AS factor
FROM terms_2118_tc_3
GROUP BY power
),
terms AS (
SELECT power,ABS(factor) AS factor,
 (CASE WHEN factor <0 THEN '-' ELSE '+' END) AS sign,
 (CASE WHEN power =1 THEN CONCAT(ABS(factor),'X')
 WHEN power =0 THEN ABS(factor)::TEXT
 ELSE CONCAT(ABS(factor),'X^',power)
 END) AS term
FROM grouped_terms
)
SELECT CONCAT(STRING_AGG(CONCAT(sign,term),''ORDER BY power DESC),'=0') AS equation
FROM terms;