Description

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You found a really old computer at your local library, and it looks like there’s still some data about old library books left on its hard drive.

After closer examination, you’ve discovered that there is a book_chapters table, which has the following structure:

• chapter_name: the name of the book’s chapter;
• chapter_number: the unique number of the chapter written as a Roman numeral.

Note that there could be gaps in chapter numbers. Also, every library book has fewer than 1000 chapters.

Here is the table of Roman numeral symbols and their values:

Symbol	Value
I	1
V	5
X	10
L	50
C	100
D	500
M	1000

After looking through the library, you’ve found what seems to be the remnants of this same book! Unfortunately its chapters are not numbered on the pages.

You decide to find the order in which you should read the books chapters by using the old computer and the information stored in the book_chapters table.

Given the book_chapters table, compose a results table that consists of a single column chapter_name that contains the names of the book’s chapters. The table should be sorted in ascending order by the chapter’s actual numbers (i.e. chapter number III should come before chapter number V).

Example

For the following tables book_chapters

chapter_name	chapter_number
A Dead Man	LVI
Behaviour in General	I
Cast Up	XLIX
Imitation	IX
Nemesis	L
Paste	XXIII
The Cub	XXI
The Oxenham Arms	XXIV
Two Bequests	XLVII

the output should be

chapter_name
Behaviour in General
Imitation
The Cub
Paste
The Oxenham Arms
Two Bequests
Cast Up
Nemesis
A Dead Man

Here are the chapter number converted to Hindu-Arabic numerals:

chapter_name	chapter_number
A Dead Man	56
Behaviour in General	1
Cast Up	49
Imitation	9
Nemesis	50
Paste	23
The Cub	21
The Oxenham Arms	24
Two Bequests	47

• [execution time limit] 10 seconds (mysql)

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/*Please add ; after each select statement*/
CREATE FUNCTION charValue (ch VARCHAR(1))
RETURNS INT
BEGIN
    RETURN CASE ch
        WHEN 'I' THEN 1
        WHEN 'V' THEN 5 
        WHEN 'X' THEN 10 
        WHEN 'L' THEN 50 
        WHEN 'C' THEN 100 
        WHEN 'D' THEN 500 
        WHEN 'M' THEN 1000
        ELSE 0
    END;
END;

CREATE FUNCTION FromRomanNumerals (romanNumeral VARCHAR(100))
RETURNS INT
BEGIN
    DECLARE numeral INT DEFAULT 0;
    DECLARE pre INT DEFAULT 0;
    DECLARE cur INT DEFAULT 0;

    SET pre = charValue(LEFT(romanNumeral, 1));
    SET numeral = charValue(LEFT(romanNumeral, 1));
    SET romanNumeral = SUBSTRING(romanNumeral, 2);
    WHILE CHAR_LENGTH(romanNumeral) > 0 DO
        SET cur = charValue(LEFT(romanNumeral, 1));
        SET numeral = numeral + cur - IF(cur > pre, pre*2,0);
        SET romanNumeral = SUBSTRING(romanNumeral, 2);
        SET pre = cur;
    END WHILE;

  RETURN numeral;
END;

CREATE PROCEDURE sortBookChapters()
BEGIN
    
    
	SELECT chapter_name FROM book_chapters ORDER BY FromRomanNumerals(chapter_number);
END