LeetCode OJ：Compare Version Numbers（比较版本字符串）

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

注意可能会出现前置0的情况，所以分为小数点钱与小数点后转换成数字来判断，代码如下：

class Solution {
public:
    int compareVersion(string version1, string version2) {
        int i1, i2;
        int val1, val2;
        for(i1 = 0, i2 = 0; i1 < version1.size() || i2 < version2.size(); ++i1, ++i2){
            val1 = 0;
            for(; i1 < version1.size(); ++i1){
                if(version1[i1] == '.')
                    break;
                val1 = val1 * 10 + version1[i1] - '0';
            }
            val2 = 0;
            for(; i2 < version2.size(); ++i2){
                if(version2[i2] == '.')
                    break;
                val2 = val2 * 10 + version2[i2] - '0';
            }
            if(val1 > val2)
                return 1;
            else if(val1 < val2) 
                return -1;
        }
        return 0;
    }
};