14. Longest Common Prefix

不断更新最长前缀，最后得到结果

class Solution {public:    string longestCommonPrefix(vector<string>& strs) {        if(strs.size()==0)            return "";        string result=strs[0];        for(int i=1;i<strs.size();i++)        {            string first=strs[i];            string second=result;            result.clear();            int indexFirst=0;            int indexSecond=0;            while(indexFirst<first.length()&&indexSecond<second.length())            {                if(first[indexFirst]==second[indexSecond])                {                    result+=first[indexFirst];                    indexFirst++;                    indexSecond++;                }                else                    break;            }        }        return result;    }};