1.说明

合并两个列表，这里list使用的是链表结构

2.代码

// Definition for singly-linked list.
function ListNode(val) {
    this.val = val;
    this.next = null;
}

/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
var mergeTwoLists = function(l1, l2) {
    var i = l1;
    var j = l2;
    var h1 = h2 = new ListNode();
    while (i && j) {
        if (i.val < j.val) {
            h2.next = i;
            h2 = h2.next;
            i = i.next;
        }
        else {
            h2.next = j;
            h2 = h2.next;
            j = j.next;
        }
    }
    if (i) {
        while (i) {
            h2.next = i;
            h2 = h2.next;
            i = i.next;
        }
    }
    if (j) {
        while (j) {
            h2.next = j;
            h2 = h2.next;
            j = j.next;
        }
    }
    return h1.next;
};