链表操作 —— 1. 2_两数相加

1. 2_两数相加

/*
输入：(2 -> 4 -> 3) + (5 -> 6 -> 4)
输出：7 -> 0 -> 8
原因：342 + 465 = 807
*/
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        if(l1 == null && l2 == null) return null;
        else if(l1 == null) return l2;
        else if(l2 == null) return l1;
        int c = 0;
        ListNode ret = new ListNode(-1);
        ListNode cur = ret;
        while(l1 != null || l2 != null || c != 0)
        {
            int val1 = (l1 == null) ? 0 : l1.val;
            int val2 = (l2 == null) ? 0 : l2.val;
            int tmp = val1 + val2 + c;
            if(tmp >= 10){
                tmp -= 10;
                c = 1;
            }else {
                c = 0;
            }
            ListNode node = new ListNode(tmp);
            cur.next = node;
            cur = cur.next;
            if(l1 != null) l1 = l1.next;
            if(l2 != null) l2 = l2.next;
        }


        return ret.next;
    }
}