1. 问题描述:
2. 解决办法:
class Solution(object):
def romanToInt(self, s):
"""
:type s: str
:rtype: int
"""
# a more efficient way to define dictionary:
# Symbol = ['I', 'V', 'X', 'L', 'C', 'D', 'M']
# Value = [1, 5, 10, 50, 100, 500, 1000]
# HashTable = dict(zip(Symbol,Value))
search_dict = {"I": 1, "V": 5, "X": 10, "L": 50, "C": 100, "D": 500, "M": 1000}
index_last = len(s) - 1
integer = search_dict[s[index_last]]
if index_last == 0:
return integer
for i in range(index_last - 1, -1, -1):
if search_dict[s[i]] < search_dict[s[i + 1]]:
integer -= search_dict[s[i]]
else:
integer += search_dict[s[i]]
return integer
3. 解决思路:
先判断是不是只有一个字符;
比后一位小的,减,否则,加
教训: 一定要好好读题,回归到简单的运算中去