HOT100——合并两个有序列表（JS实现）

var mergeTwoLists = function(l1, l2) {
    // 首先两个链表都是升序的，我们可以考虑双指针
    let left = l1;
    let right = l2;
    const node = new ListNode();
    let head = node;
    while (left && right) {
        if (left.val < right.val) {
            head.next = left;
            left = left.next; 
            head = head.next;
        } else {
            head.next = right;
            right = right.next;
            head = head.next;
        }
    }
    if (!left && right) {
        head.next = right;
    }
    if (!right && left) {
        head.next = left;
    }
    return node.next
};