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
给你两个链表，这两个链表代表两个数字，从头到尾为低位到高位。
这两个数做相加，然后以同样形式的链表返回结果
同时遍历两个链表，同时逐位建立结果链表
var addTwoNumbers = function(l1, l2) {
var up = 0;
var head = null;
var last = null;
var head1 = l1;
var head2 = l2;
while (head1||head2) {
let a = head1 ? head1.val : 0;
let b = head2 ? head2.val : 0;
let res = up + a + b;
up = parseInt(res/10);
res = res%10;
res = new ListNode(res);
if (head) {
last.next = res;
last = res;
} else {
head = res;
last = res;
}
if (head1) head1 = head1.next;
if (head2) head2 = head2.next;
}
if (up!==0) {
let res = new ListNode(up);
last.next = res;
last = res;
}
return head;
};
