Compare Version Numbers - LintCode

描述
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.

樣例
Here is an example of version numbers ordering:

0.1 < 1.1 < 1.2 < 13.37

思路
遍歷字符串，提取點號間的字符串並進行比較，若不同，返回結果；否則，繼續提取下兩個字符串。

#ifndef C1352_H
#define C1352_H
#include<iostream>
#include<string>
using namespace std;
class Solution {
public:
    /**
    * @param version1: the first given number
    * @param version2: the second given number
    * @return: the result of comparing
    */
    int compareVersion(string &version1, string &version2) {
        // Write your code here
        int len1 = version1.size(), len2 = version2.size();
        int i = 0, j = 0;
        string str1, str2;//表示點號間的子串
        bool flag1 = false, flag2 = false;//表示是否經歷了點號
        while (i < len1||j < len2)
        {
            if (i<len1 && version1[i] != '.')
            {
                if (flag1)
                {
                    flag1 = false;
                    str1.clear();
                }
                str1 += version1[i];
                ++i;
            }
            else
                flag1 = true;
            if (j<len2 && version2[j] != '.')
            {
                if (flag2)
                {
                    flag2 = false;
                    str2.clear();
                }
                str2 += version2[j];
                ++j;
            }
            else
                flag2 = true;
            //當兩者都在點號上,比較字符串的大小
            if (flag1&&flag2)
            {
                int temp = strCompare(str1, str2);
                if (temp > 0)
                    return 1;
                else if (temp < 0)
                    return -1;
                else
                {
                    ++i;
                    ++j;
                }
            }
        }
        return strCompare(str1,str2);
    }
    //判斷str1和str2的大小,str1>str2,返回1;str1<str2,返回-1;相等返回0
    int strCompare(string &str1, string &str2)
    {
        //在字符串前面加'0',使得二者長度相等
        int len1 = str1.size(), len2 = str2.size();
        if (len1 > len2)
        {
            for (int i = 0; i < len1 - len2; ++i)
                str2 = '0' + str2;
        }
        else
        {
            for (int i = 0; i < len2 - len1; ++i)
                str1 = '0' + str1;
        }
        //比較字符串
        int size = str1.size();
        for (int i = 0; i < size; ++i)
        {
            if (str1[i]>str2[i])
                return 1;
            else if (str1[i] < str2[i])
                return -1;
        }
        return 0;
    }
};
#endif