Leetcode 2 Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

 

解题思路:

新建一个链表, 然后一位一位相加, 注意进位的处理就好~还有最后一个节点相加的时候, 有进位要加上去.

给p.next赋值的时候要new ListNode啊..别傻傻的直接等于..跟我似的..lol

 

public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    if(l1 == null)
            return l2;
        if(l2 == null)
            return l1;
        int add = 0;
        ListNode head = new ListNode(0);
        ListNode p = head;
        
        while(l1 != null && l2 != null){
            p.next = new ListNode((l1.val + l2.val + add) % 10);
            add = (l1.val + l2.val + add) / 10;
            l1 = l1.next;
            l2 = l2.next;
            p = p.next;
        }
        while(l1 != null && l2 == null){
            p.next = new ListNode((l1.val + add) % 10);
            add = (l1.val + add) / 10;
            l1 = l1.next;
            p = p.next;
        }
        while(l1 == null && l2 != null){
            p.next = new ListNode((l2.val + add) % 10);
            add = (l2.val + add) / 10;
            l2 = l2.next;
            p = p.next;
        }
        if(add == 1){
            p.next = new ListNode(1);
            
        }
        return head.next;
}