Leetcode_2. Add_Two_Number

2. Add_Two_Number

用两个非空链表分别表示两个非负整数，链表的节点表示数字的位，链表头表示数字的低位，链表尾表示数字高位。求两个链表所表示数字的和。

比如:

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

/**
 * Definition for singly-linked list.
 * type ListNode struct {
 *     Val int
 *     Next *ListNode
 * }
 */
func addTwoNumbers(l1 *ListNode, l2 *ListNode) *ListNode {
   
    var over = 0
    var head, tmp *ListNode
    for l1 != nil && l2 != nil {
        if head == nil {
            tmp = new(ListNode)
            head = tmp
        } else {
            tmp.Next = new(ListNode)
            tmp = tmp.Next
        }
        tmp.Val = l1.Val + l2.Val + over
        over = tmp.Val / 10
        tmp.Val -= over * 10
        l1 = l1.Next
        l2 = l2.Next
    }

    for l1 != nil {
        if head == nil {
            tmp = new(ListNode)
            head = tmp
        } else {
            tmp.Next = new(ListNode)
            tmp = tmp.Next
        }

        tmp.Val = l1.Val + over
        over = tmp.Val / 10
        tmp.Val -= over * 10

        l1 = l1.Next
    }

    for l2 != nil {

        if head == nil {
            tmp = new(ListNode)
            head = tmp
        } else {
            tmp.Next = new(ListNode)
            tmp = tmp.Next
        }

        tmp.Val = l2.Val + over
        over = tmp.Val / 10
        tmp.Val -= over * 10

        l2 = l2.Next
    }

    if over != 0 {
        if tmp == nil {
            tmp = new(ListNode)
            head = tmp
        } else {
            tmp.Next = new(ListNode)
            tmp = tmp.Next
        }
        tmp.Val = over
    }

    return head
}