LeetCode 14: Longest Common Prefix

string CommonPrefix(string str1,string str2)
{
    int len_1=str1.length();
    int len_2=str2.length();

    int min_len=len_1>len_2 ? len_2:len_1;

    string s="";
    for(int i=0;i<min_len;++i)
    {
        if (str1[i]==str2[i])
            s+=str1[i];
        else
            break;
    }
    return s;
}

string longestCommonPrefix(vector<string>& strs)
{
    if (strs.size() == 0)
        return "";
    string s=strs[0];
    for (int i=1;i<strs.size();++i)
    {
        s=CommonPrefix(s,strs[i]);
        if (s=="")
            break;
    }
    return s;
}