2.html

<script>
    function ListNode(val) {
        this.val = val;
        this.next = null;
    }

    /**
     * 给出两个 非空 的链表用来表示两个非负的整数。其中，它们各自的位数是按照 逆序 的方式存储的，并且它们的每个节点只能存储 一位 数字。

     如果，我们将这两个数相加起来，则会返回一个新的链表来表示它们的和。

     您可以假设除了数字 0 之外，这两个数都不会以 0 开头。
     /**
     * @param {ListNode} l1
     * @param {ListNode} l2
     * @return {ListNode}
     */
/*    var addTwoNumbers = function (l1, l2) {
        let currNode1 = l1;
        let currNode2 = l2;
        // 标记是否进位
        let carryFlag = 0;
        while (true) {
            currNode1.val += currNode2.val + carryFlag;
            if (currNode1.val < 10) {
                carryFlag = 0;
            } else {
                currNode1.val -= 10;
                carryFlag = 1;
            }
            if (currNode1.next === null || currNode2.next === null) {
                break;
            }
            currNode1 = currNode1.next;
            currNode2 = currNode2.next;
        }
        if (currNode2.next !== null) {
            currNode1.next = currNode2.next;
        }
        while (carryFlag > 0) {
            if (currNode1.next === null) {
                currNode1.next = new ListNode(carryFlag);
                break;
            }
            let newVal = currNode1.next.val + carryFlag;
            if (newVal < 10) {
                currNode1.next.val = newVal;
                carryFlag = 0;
            } else {
                currNode1.next.val = newVal - 10;
                carryFlag = 1;
                currNode1 = currNode1.next;
            }
        }
        return l1;
    };*/
    var addTwoNumbers = function (l1, l2) {
        let bak = new ListNode(null);
        let node = bak;
        let carryNum = 0;
        while (l1 !== null && l2 !== null) {
            let newVal = l1.val + l2.val + carryNum;
            let newNode;
            if (newVal < 10) {
                newNode = new ListNode(newVal);
                carryNum = 0;
            } else {
                newNode = new ListNode(newVal % 10);
                carryNum = 1;
            }
            node.next = newNode;
            node = newNode;
            l1 = l1.next;
            l2 = l2.next;
        }
        if (l1 !== null) {
            node.next = l1;
        } else if (l2 !== null) {
            node.next = l2;
        }
        while (carryNum > 0) {
            if (node.next === null) {
                node.next = new ListNode(carryNum);
                break;
            }
            let newVal = node.next.val + carryNum;
            if (newVal < 10) {
                node.next.val = newVal;
                carryNum = 0;
            } else {
                node.next.val = newVal % 10;
                carryNum = 1;
                node = node.next;
            }
        }
        return bak.next;
    };
    // let result = addTwoNumbers([2, 4, 3], [5, 6, 4]);
    // let result = addTwoNumbers(new ListNode(9), new ListNode(9));
    /*    let listNode = new ListNode(9);
        listNode.next = new ListNode(8);
        let result = addTwoNumbers(listNode, new ListNode(1));*/
    let listNode = new ListNode(7);
    listNode.next = new ListNode(9);
    let result = addTwoNumbers(new ListNode(0), listNode);
    console.log(result)
</script>