21.merge-two-sorted-lists.js

/*
 * @lc app=leetcode id=21 lang=javascript
 *
 * [21] Merge Two Sorted Lists
 */

// @lc code=start
/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} list1
 * @param {ListNode} list2
 * @return {ListNode}
 */
var mergeTwoLists = function(list1, list2) {
    var head = new ListNode();
    var current = head;
    while (list1 != null && list2 != null) {
        if (list1.val < list2.val) {
            current.next = list1;
            list1 = list1.next;
        } else {
            current.next = list2;
            list2 = list2.next;
        }
        current = current.next;
    }
    if (list1 != null) {
        current.next = list1;
    }
    if (list2 != null) {
        current.next = list2;
    }
    return head.next;
};
// @lc code=end