Problem Statement

You are given two non-empty linked lists that represent two non-negative integers, where each node contains the single digit. The digits are stored in reverse order. Add these two numbers and return the sum as a linked list.

You can assume the numbers do not have leading zeros, except for the number 0 itself.

Examples

Example 1:

• Input: l1: [1, 2, 3], l2: [4, 5, 6]
• Expected Output: [5, 7, 9]
• Justification: 321 + 654 = 975, which in reverse order is [5, 7, 9].

Example 2:

• Input: l1: [7, 8], l2: [6, 7, 8, 9]
• Expected Output: [3, 6, 9, 9]
• Justification: 87 + 9876 = 9963, which in reverse order is [3, 6, 9, 9].

Example 3:

• Input: l1: [0], l2: [0]
• Expected Output: [0]
• Justification: 0 + 0 = 0, which in reverse order is [0].

Constraints:

• The number of nodes in each linked list is in the range [1, 100].
• 0 <= Node.val <= 9
• It is guaranteed that the list represents a number that does not have leading zeros.

Try it yourself

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