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.