leetcode-21-java

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing 
together the nodes of the first two lists.

Example:

Input: 1->2->4, 1->3->4
Output: 1->1->2->3->4->4

/**
 * Input: 1->2->4, 1->3->4
 * Output: 1->1->2->3->4->4
 * @param l1
 * @param l2
 * @return
 */
public static ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    ListNode dummy = new ListNode(0);
    ListNode cursor = dummy;
    while (null != l1 || null != l2) {

        if ((null != l1 && null != l2 && l1.val <= l2.val) ||
                (null != l1 && null == l2)) {
            cursor.next = l1;
            l1 = l1.next;
        } else {
            cursor.next = l2;
            l2 = l2.next;
        }
        cursor = cursor.next;
    }
    return dummy.next;
}

private static class ListNode {
    int val;
    ListNode next;

    ListNode(int x) {
        val = x;
    }
}