Write a function to find the longest common prefix string amongst an array of strings.
to compare all the strings assume the longest_prefix's length is m and there are n strings. we will need at least o(mn) time.
class Solution(object):
def longestCommonPrefix(self, strs):
"""
:type strs: List[str]
:rtype: str
"""
if not strs:
return ''
longest_string = min(strs)
for index in range(len(longest_string)):
for string in strs:
if longest_string[index] != string[index]:
return longest_string[:index] if index > 0 else ''
return longest_string