[LeetCode]Compare Version Numbers

Compare Version Numbers

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

Credits:
Special thanks to @ts for adding this problem and creating all test cases.

解题思路：

这道题思路倒是挺简单的，按每个‘.’进行分割，逐个比较大小即可。但是要考虑不是同样多个‘.’和1.0与1.0.0等情况。

代码如下：

class Solution {public:    int compareVersion(string version1, string version2) {        string leftVersion1 = version1;        string leftVersion2 = version2;        while(leftVersion1!=""&&leftVersion2!=""){            int subver1, subver2;                        int pos1 = leftVersion1.find('.');            if(pos1!=string::npos){                subver1 = strToInt(leftVersion1.substr(0, pos1));                leftVersion1 = leftVersion1.substr(pos1 + 1);            }else{                subver1 = strToInt(leftVersion1);                leftVersion1 = "";            }                        int pos2 = leftVersion2.find('.');            if(pos2!=string::npos){                subver2 = strToInt(leftVersion2.substr(0, pos2));                leftVersion2 = leftVersion2.substr(pos2 + 1);            }else{                subver2 = strToInt(leftVersion2);                leftVersion2 = "";            }                        if(subver1>subver2){                return 1;            }            if(subver1<subver2){                return -1;            }        }        if(leftVersion1!=""&&!checkAllZero(leftVersion1)){            return 1;        }        if(leftVersion2!=""&&!checkAllZero(leftVersion2)){            return -1;        }        return 0;    }private:    int strToInt(string s){        int base = 1;        int result = 0;        int len = s.length();        for(int i=len-1;i>=0; i--){            result += base*(s[i]-'0');            base *= 10;        }        return result;    }    bool checkAllZero(string s){        int len = s.length();        for(int i = 0; i<len; i++){            if(s[i]!='.' && s[i]!='0'){                return false;            }        }        return true;    }};