very surprised to beat 100%, surely many others have done the same before? are the timings correct?

```
def minDistance(self, word1, word2):
return self.edit_distance(word1, len(word1)-1, word2, len(word2)-1, {})
def edit_distance(self, word1, i, word2, j, memo): # i, j are next indices to be matched
if i < 0 or j < 0: # one string is empty (already matched), return remaining length of other
return i + 1 + j + 1
if (i, j) in memo:
return memo[(i, j)]
if word1[i] == word2[j]:
result = self.edit_distance(word1, i-1, word2, j-1, memo)
else:
result = 1 + min(self.edit_distance(word1, i-1, word2, j, memo),
self.edit_distance(word1, i, word2, j-1, memo),
self.edit_distance(word1, i-1, word2, j-1, memo))
memo[(i, j)] = result
return result
```