Python/2._Add_Two_Numbers.ipynb

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    "# 2. Add Two Numbers\n",
    "\n",
    "You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each of their nodes contains a single digit. Add the two numbers and return the sum as a linked list.\n",
    "\n",
    "You may assume the two numbers do not contain any leading zero, except the number 0 itself.\n",
    "\n",
    "### Example 1:\n",
    "\n",
    "Input: l1 = [2,4,3], l2 = [5,6,4]\n",
    "Output: [7,0,8]\n",
    "Explanation: 342 + 465 = 807.\n",
    "\n",
    "### Example 2:\n",
    "\n",
    "Input: l1 = [0], l2 = [0]\n",
    "Output: [0]\n",
    "\n",
    "### Example 3:\n",
    "\n",
    "Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]\n",
    "Output: [8,9,9,9,0,0,0,1]\n",
    " \n",
    "### Constraints:\n",
    "\n",
    "The number of nodes in each linked list is in the range [1, 100].\n",
    "0 <= Node.val <= 9\n",
    "It is guaranteed that the list represents a number that does not have leading zeros."
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    "# Definition for singly-linked list.\n",
    "class ListNode:\n",
    "    def __init__(self, val=0, next=None):\n",
    "        self.val = val\n",
    "        self.next = next\n",
    "class Solution:\n",
    "    def addTwoNumbers(self, l1: Optional[ListNode], l2: Optional[ListNode]) -> Optional[ListNode]:\n",
    "        dummy=ListNode()\n",
    "        curr=dummy\n",
    "        carry=0\n",
    "        while l1 or l2 or carry:\n",
    "            if l1:\n",
    "                carry+=l1.val\n",
    "                l1=l1.next\n",
    "            if l2:\n",
    "                carry+=l2.val\n",
    "                l2=l2.next\n",
    "            curr.next=ListNode(carry%10)\n",
    "            curr=curr.next\n",
    "            carry//=10\n",
    "        return dummy.next"
   ]
  }
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