原题链接14. Longest Common Prefix
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.

解题思路: 暴力求解，注意边界条件

func longestCommonPrefix(strs []string) string {
    if len(strs) == 0 {
        return ""
    }
    res := ""
    for i, v := range strs[0] {
        c := byte(v)
        for _, s := range strs {
            if len(s) < i+1 || s[i] != c {
                return res
            }
        }
        res += string(c)
    }
    return res   
}