Leetcode------Roman to Integer

Title:	Roman to Integer
Pass Rate:	34.1%
Difficulty:	Simple

Given a Roman numeral, convert it to an integer.

Input is guaranteed to being within the range from 1 to 3999.

The whole is not very difficult, that is, to convert a string of Roman numerals into Arabic, mainly to the understanding of Roman numerals. I don't know anything about the meaning of Roman numerals first:

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

In general are from large to small writing, and then add the line, but there will be a few special, such as Iv:5, cd:400, and so on, these are small in front, large reduction can be,

So the idea is to deal with the string from the back forward, the overall order is i:[length-1]->[0], each time comparing the position I and the i+1 position, if I position <i+1 position then use and value minus I position, and so on. There is no robustness to consider, the topic has been said to be in the 1-3999 string. Only processing is empty when the return 0 on the line, the specific algorithm to see the code:

1  Public classSolution {2      Public intRomantoint (String s) {3Map<character,integer> map=NewHashmap<character,integer>();4Map.put (' I ', 1);5Map.put (' V ', 5);6Map.put (' X ', 10);7Map.put (' L ', 50);8Map.put (' C ', 100);9Map.put (' D ', 500);TenMap.put (' M ', 1000); One         intLength=s.length (), result=0; A         if(length==0)return0; -Result=map.get (S.charat (length-1)); -Length=length-2; the          while(length>=0){ -             if(Map.get (S.charat (length)) <map.get (S.charat (length+1))) -             { -result-=Map.get (S.charat (length)); +length--; -             } +             Else{ Aresult+=Map.get (S.charat (length)); atlength--; -             } -                  -              -         } -         returnresult; in } -}

Leetcode------Roman to Integer