```
def plusOne(self, digits):
return [int(i) for i in str(reduce(lambda x,y: x*10+y, digits) + 1)]
def plusOne(self, digits):
return [int(i) for i in str(int("".join([str(i) for i in digits])) + 1)]
def plusOne(self, digits):
if not digits:
return [1]
elif digits[-1] == 9:
return self.plusOne(digits[:-1])+[0]
else:
digits[-1] += 1
return digits
```