8.leetcode题目165： Compare Version Numbers

题目：

Compare two version numbers version1 and version2.

If version1 > version2 return 1, if version1 < version2 return -1, otherwise return 0.

You may assume that the version strings are non-empty and contain only digits and the 

.

 character.

The 

.

 character does not represent a decimal point and is used to separate number sequences.

For instance, 

2.5

 is not "two and a half" or "half way to version three", it is the fifth
second-level revision of the second first-level revision.

Here is an example of version numbers ordering: 

0.1 < 1.1 < 1.2 < 13.37

分析：

比较版本号大小，2.5表示第2版第5个。

将字符串转换为整数，一段一段比较

while(i<version1.length()||j<version2.length())

这句比较好

我的一个问题：：
字符转数字的时候，总是忘了减去‘0’