from typing import List


def getLongestCommonPrefix(strs: List[str]) -> str:
    """
    >>> getLongestCommonPrefix(["abc_aaa","abc_bb","abc_aaaa"])
    'abc_'
    >>> getLongestCommonPrefix(["b","abc_bb","abc_aaaa"])
    ''
    >>> getLongestCommonPrefix([])
    ''
    """
    l = len(strs)
    if l == 0:
        return ""
    else:
        m = min(map(len, strs))
        if m == 0:
            return ""

        for i in range(0, m):
            common = strs[0][i]
            for s in strs:
                if s[i] != common:
                    return strs[0][0:i]
        return strs[0]