• first attempt

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if(strs.size()==0)
            return "";
        if(strs.size()==1)
            return strs[0];
        string common="";
        int twomin= strs[0].size()<strs[1].size()?strs[0].size():strs[1].size();
        for(int i = 0 ; i <twomin ; i++)
            if(strs[0][i]==strs[1][i])
                common+=strs[0][i];
            else
                break;
        for(int j = 2; j < strs.size() ; j++)
            while(strs[j].compare(0,common.size(),common)!=0)
            {
                common.pop_back();
            }
         return common; 
    }
};