Write a function to find the longest common prefix string amongst an array of strings.

If there is no common prefix, return an empty string "".

Example 1:

Input: ["flower","flow","flight"]
Output: "fl"

Example 2:

Input: ["dog","racecar","car"]
Output: ""
Explanation: There is no common prefix among the input strings.

Note:

All given inputs are in lowercase letters a-z.

尋找最長公共字首，可以將後面的字串依次與首個字串比較，有不同的就停止比較，將相同的部分存入陣列返回

class Solution {
public:
    string longestCommonPrefix(vector<string>& strs) {
        if(strs.empty())
            return "";
        for(int i=0; i<strs[0].size(); i++)
        {
            for(int j=1; j<strs.size(); j++)
            {
                if(strs[j][i] != strs[0][i])
                    strs[0] = strs[0].substr(0,i);//複製長度為i的字串
            }
        }
          return strs[0];  
        
    }
};