13. Roman to Integer
Problem:
Roman numerals are represented by seven different symbols: I
, V
, X
, L
, C
, D
and M
.
For example, two is written as II
in Roman numeral, just two one's added together. Twelve is written as, XII
, which is simply X
+ II
. The number twenty seven is written as XXVII
, which is XX
+ V
+ II
.
Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII
. Instead, the number four is written as IV
. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX
. There are six instances where subtraction is used:
I
can be placed beforeV
(5) andX
(10) to make 4 and 9.X
can be placed beforeL
(50) andC
(100) to make 40 and 90.C
can be placed beforeD
(500) andM
(1000) to make 400 and 900.
Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
Example 1:
Example 2:
Example 3:
Example 4:
Example 5:
Solution:
Normally we just add up the digits, except when the digit is greater than its left (e.g. IV). In that case we need to fallback and remove the last digit then combine the two as new digit. That is why we subtract the last digit twice.
☆*: .。. o(≧▽≦)o .。.:☆☆: .。. o(≧▽≦)o .。.:☆☆: .。. o(≧▽≦)o .。.:*☆
☆*: .。. o(≧▽≦)o .。.:☆☆: .。. o(≧▽≦)o .。.:*☆
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