Add comprehensive LeetCode solutions index documentation

src/exercises/2.add-two-numbers.py

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+from string import *
+from re import *
+from datetime import *
+from collections import *
+from heapq import *
+from bisect import *
+from copy import *
+from math import *
+from random import *
+from statistics import *
+from itertools import *
+from functools import *
+from operator import *
+from io import *
+from sys import *
+from json import *
+from builtins import *
+import string
+import re
+import datetime
+import collections
+import heapq
+import bisect
+import copy
+import math
+import random
+import statistics
+import itertools
+import functools
+import operator
+import io
+import sys
+import json
+from typing import *
+
+
+# @leet start
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def node(self, val, next=None):
+        self.val = val
+        self.next = next
+
+    def addTwoNumbers(
+        self, l1: Optional[ListNode], l2: Optional[ListNode]
+    ) -> Optional[ListNode]:
+        carry = 0
+        value_l1 = l1
+        value_l2 = l2
+        head = None
+        tail = None
+        while value_l1 or value_l2:
+            l2_val = l2.val if l2 else 0
+            l1_val = l1.val if l1 else 0
+            addition = l1_val + l2_val + carry
+            if addition > 9:
+                temp = str(addition)
+                carry = int(temp[0])
+                addition = int(temp[1])
+            else:
+                carry = 0
+            new_node = ListNode(addition)
+            if head is None:
+                head = new_node
+                tail = new_node
+            else:
+                tail.next = new_node
+                tail = new_node
+            value_l1 = l1.next if l1 else None
+            value_l2 = l2.next if l2 else None
+            l1 = l1.next if l1 else None
+            l2 = l2.next if l2 else None
+        if carry > 0:
+            new_node = ListNode(carry)
+            tail.next = new_node
+            tail = new_node
+
+        return head
+
+
+# @leet end