[leetcode-in-go] 0002-Add Two Numbers

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 contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

解题思路

从左到右相加即可，注意进位，注意缺位补全

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {

	// head 追溯结果，carry 记录进位
	head, carry := &ListNode{}, 0
	p := head

	for l1 != nil || l2 != nil || carry != 0 {
        if l1 == nil {
            l1 = &ListNode{0, nil}
        }
        if l2 == nil {
            l2 = &ListNode{0, nil}
        }
		sum := l1.Val + l2.Val + carry
		carry = sum / 10
		val := sum % 10
		p.Next = &ListNode{val, nil}
		p = p.Next
		l1 = l1.Next
		l2 = l2.Next
	}

	return head.Next
}