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.

Python

 
class Solution(object):
    def longestCommonPrefix(self, strs):
        """
        :type strs: List[str]
        :rtype: str
        """
        result_str = ""
        if strs is not None and len(strs) > 0:
            strs.sort()
            str_first = strs[0]
            str_last = strs[len(strs)-1]
            a = 0
            for i in str_first:
                if i == str_last[a]:
                    result_str += i
                    a += 1
                else:
                    return result_str
        return result_str

csharp

 
public class Solution {
    public string LongestCommonPrefix(string[] strs) {
        string result_str = "";
            if (strs != null && strs.Length > 0)
            {
                Array.Sort(strs);
                string str_first = strs[0];
                string str_last = strs[strs.Length - 1];
                int a = 0;
                foreach(var i in str_first)
                {
                    if (string.Equals(i,str_last[a]))
                    {
                        result_str += i;
                        a++;

                    }
                    else
                    {
                        return result_str;
                    }
                }

            }

            return result_str;
    }
}