MergeTwoSortedLists.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.
 */
public class MergeTwoSortedLists {
  public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    ListNode head = new ListNode(0);
    ListNode cur = head;
    while (l1 != null && l2 != null) {
      if (l1.val <= l2.val) {
        cur.next = l1;
        l1 = l1.next;
      } else {
        cur.next = l2;
        l2 = l2.next;
      }
      cur = cur.next;
    }
    if (l1 != null) {
      cur.next = l1;
    } else {
      cur.next = l2;
    }
    return head.next;
  }
}