腾讯五十题No.1

力扣题目链接

class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode root = new ListNode(0);
        ListNode cursor = root;
        //保存进位值
        int carry = 0;
        while(l1 != null || l2 != null || carry != 0){
            int l1val = l1 != null? l1.val : 0;
            int l2val = l2 != null? l2.val : 0;
            int sum = l1val + l2val + carry;
            carry = sum/10;
            ListNode sumNode = new ListNode(sum % 10);
            cursor.next = sumNode;
            cursor = sumNode;
            if(l1 != null) l1 = l1.next;
            if(l2 != null) l2 = l2.next;
        }
        return root.next;
    }
}

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