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LeetCode: Add Two Numbers Python 3 iterative solution
Here's my solution for the add two numbers problem on LeetCode.
Input: (2 -> 4 -> 3) + (5 -> 6 -> 4) Output: 7 -> 0 -> 8 Explanation: 342 + 465 = 807.
When doing problems on websites such as LeetCode, I like to code in my own IDE, that's why you'll see some additional helper functions besides the solution code.
class Solution(object): def _get_append_func(self, root): _root = root def __add_to_list(value): nonlocal _root _root.next = ListNode(value) _root = _root.next return __add_to_list def _compute(self, result, base=10): carry = result // base rest = result % base return carry, rest def addTwoNumbers(self, l1, l2): """ :type l1: ListNode :type l2: ListNode :rtype: ListNode """ root_node = None root_append_func = None term_1 = l1 term_2 = l2 saved_carry = 0 while True: # end of expression ; add cary if any if term_1 is None and term_2 is None: if saved_carry > 0: root_append_func(saved_carry) break # We haven't reached the end, we assume that whatever term is left is 0 if term_1 is None: term_1 = ListNode(0) if term_2 is None: term_2 = ListNode(0) # add the two terms term_sum_carry, term_sum_no_carry = self._compute(term_1.val + term_2.val) # add sum to current carry next_carry, total_with_carry = self._compute(term_sum_no_carry + saved_carry) # save carry saved_carry = term_sum_carry + next_carry # save total if not root_node: root_node = ListNode(total_with_carry) root_append_func = self._get_append_func(root_node) else: root_append_func(total_with_carry) # move on term_1 = term_1.next term_2 = term_2.next return root_node
My solution isn't that great because of the _add_to_list function which iterates the root_node to append the next value. I have no idea how to optimize that right now.
I've learnt about nonlocal and found a way to slightly optimize my code:
def _get_append_func(self, root): _root = root def __add_to_list(value): nonlocal _root _root.next = ListNode(value) _root = _root.next return __add_to_list
Thanks for reading!