day35（12.16）——leetcode面试经典150

2. 两数相加

2. 两数相加

这道题唯一的难点就是cur如何往后移

题目：

题解：

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode list  = new ListNode(0);
        ListNode cur = list;
        int y = 0;
        while(l1 != null && l2 != null) {
            cur.next = new ListNode((l1.val + l2.val + y) % 10);
            y = (l1.val + l2.val + y) / 10;  
            l1 = l1.next;
            l2 = l2.next;
            cur = cur.next;
        }
        while(l1 != null) {
            cur.next = new ListNode((l1.val + y) % 10);
            y = (l1.val + y) / 10; 
            l1 = l1.next;
            cur = cur.next;
        }
        while(l2 != null) {
            cur.next = new ListNode((l2.val + y) % 10);
            y = (l2.val + y) / 10;
            l2 = l2.next;
            cur = cur.next;
        }
        if(y != 0) {
            cur.next = new ListNode(y);
            cur = cur.next;
        }
        //当前头是虚拟头，所以真正的链表是next之后的
        return list.next;
    }
}