longest common prefix leetcode

# 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 "".
# https://leetcode.com/problems/longest-common-prefix/

class Solution:
    def longestCommonPrefix(self, strs: List[str]) -> str:
        all = []
        for s in strs:
            for i in range(len(s)):
                all.append(s[0:(len(s)-i)])
                        
        d = {}
        for x in all:
            if x in d:
                d[x] = d[x] + 1
            else:
                d[x] = 1
                
        longest = ""
        for key in d.keys():
            if d[key] == len(strs):
                longest = key if len(longest) < len(key) else longest
                
        return longest