14. 最长公共前缀

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        string ret;
        int pos=0;
        while(1)
        {
            if(pos>=strs[0].size()) return ret;
            //设置一个初始值
            char ch=strs[0][pos];
            //遍历所有的字符串
            for(auto& s:strs)
            {
                if(pos>=s.size()||ch!=s[pos]) return ret;
            }
            pos++;
            ret+=ch;
        }
        return ret;
    }
};