代码

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var addTwoNumbers=function(l1, l2) {
	let dummyHead = new ListNode(0), node=dummyHead;
	let overflow=0, a, b, c, val;
	while(l1!==null || l2!==null) {
		a=(l1===null)?0:l1.val;
		b=(l2===null)?0:l2.val;
		c=a+b+overflow;
		val=c%10;
		overflow=Math.floor(c/10);
		node.next=new ListNode(val);
		node=node.next;
		if(l1!==null) l1=l1.next;
		if(l2!==null) l2=l2.next;
	}
	if(overflow!==0) {
		node.next=new ListNode(overflow);
	}
	return dummyHead.next;
}