Q5

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:   strs = ["flower","flow","flight"]

 Output: "fl" 

Example 2: 

 Input: strs = ["dog","racecar","car"]

 Output: "" 

Explanation: There is no common prefix among the input strings. 

 Constraints: 1 <= strs.length <= 200 0 <= strs[i].length <= 200 strs[i] consists of only lower-case English letters.