human
Write me a Python code to find the longest string in the dictionary that can be formed by deleting some characters of the given string given the following:
I found an interesting problem on https://leetcode.com/problems/longest-word-in-dictionary-through-deleting/:
Given a string and a string dictionary, find the longest string in the dictionary that can be formed by deleting some characters of the given string. If there are more than one possible results, return the longest word with the smallest lexicographical order. If there is no possible result, return the empty string.

Example 1:

Input:
s = "abpcplea", d = ["ale","apple","monkey","plea"]

Output: 
"apple"



Example 2:

Input:
s = "abpcplea", d = ["a","b","c"]

Output: 
"a"


Note:

All the strings in the input will only contain lower-case letters.
The size of the dictionary won't exceed 1,000.
The length of all the strings in the input won't exceed 1,000.

I tried it in Python, but could not do it. Can you solve it?
assistant
#Here is Python code to find the longest string in the dictionary that can be formed by deleting some characters of the given string.

class Solution:
     def findLongestWord(self, s, d):
         """
         :type s: str
         :type d: List[str]
         :rtype: str
         """
         word_dict = collections.defaultdict(list)
         for i, word in enumerate(d):
             word_dict[word[0]].append((i, word))
         
         res = ""
         for c in s:
             words_startswithc = word_dict[c]
             word_dict[c] = []
             for i, word in words_startswithc:
                 if len(word)==1: 
                     if len(d[i])==len(res):
                         res = min(res, d[i])
                     else: res = d[i] if len(d[i])>len(res) else res
                 else:
                     word_dict[word[1]].append((i, word[1:]))
         return res