《LeetBook》leetcode题解(13):Roman to Integer[E]

时间:2023-12-25 21:29:19

我现在在做一个叫《leetbook》的免费开源书项目,力求提供最易懂的中文思路,目前把解题思路都同步更新到gitbook上了,需要的同学可以去看看
书的地址:https://hk029.gitbooks.io/leetbook/

《LeetBook》leetcode题解(13):Roman to Integer[E]

013. Roman to Integer

问题

Given a roman numeral, convert it to an integer.

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

Subscribe to see which companies asked this question

思路

首先要知道罗马数字的规律:

Symbol Value
I 1
V 5
X 10
L 50
C 100
D 500
M 1,000

然后还有一个规则是,罗马数字从左自右相加,但是如果小数字A在大数字B之前,表示B-A

VI = 5+1 = 6
IV = 5-1 = 4

因此,利用2个变量保存当前数字和之前的数字就行了。因为这题很简单,用python比较方便,我就用python做的

class Solution(object):
def romanToInt(self, s):
sum=0
pre = 2000
cur = 0
Map = {'I':1,'V':5,'X':10,'L':50,'C':100,'D':500,'M':1000}
for i in range(len(s)):
cur = Map[s[i]]
sum = sum+Map[s[i]]
if cur > pre :
sum = sum-2*pre
pre = cur
return sum