8 两数相加

2. 两数相加 - 力扣（LeetCode）

题解：模拟

我们直接将两个头节点的值取出进行相加即可，相加完之后取余（就是只拿个位数的值），然后将其生成一个节点，穿起来即可，同时要记录其十位数字与下一次的链表头节点进行相加，这样一直迭代下去就可以了

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        if(l1 == null) return l2;
        if(l2 == null) return l1;
        ListNode head = new ListNode(0);
        ListNode result = head;
        int record = 0;
        while(l1 != null && l2 != null) {
            int sum = l1.val+l2.val + record;
            int count = sum % 10;
            record = sum / 10;
            head.next = new ListNode(count);
            head = head.next;
            l1 = l1.next;
            l2 = l2.next;
        }
        while(l1 != null){
            int sum = l1.val + record;
            int count = sum % 10;
            record = sum / 10;
            head.next = new ListNode(count);
            head = head.next;
            l1 = l1.next;
        }
        while(l2 != null) {
            int sum = l2.val + record;
            int count = sum % 10;
            record = sum / 10;
            head.next = new ListNode(count);
            head = head.next;
            l2 = l2.next;
        }
        if(record != 0){
            head.next = new ListNode(record);
        }
        return result.next;
    }
}