剑指Offer-17

题目：

输入两个递增排序的链表，合并这两个链表并使新链表中的结点仍然是按照递增排序的。

实现

// coding = javapublic class Solution17 {    //法1 非递归实现    public Node mergeList1(Node head1,Node head2){        if(head1==null && head2==null){            return null;        }        if(head1==null){            return head2;        }        if(head2==null){            return head1;        }        Node head;        if(head1.value<=head2.value){            head = head1;            head1 = head1.next;        }        else {            head = head2;            head2 = head2.next;        }        Node cur_node = head;        while (head1!=null && head2!=null){            if(head1.value<=head2.value){                cur_node.next = head1;                head1 = head1.next;            }            else {                cur_node.next = head2;                head2=head2.next;            }            cur_node = cur_node.next;        }        while(head1!=null){            cur_node.next = head1;            head1 = head1.next;            cur_node = cur_node.next;        }        while (head2!=null){            cur_node.next = head2;            head2 = head2.next;            cur_node = cur_node.next;        }        cur_node.next=null;        return head;    }    //法2 递归实现    public Node mergeList2(Node head1,Node head2){        if(head1==null){            return head2;        }        else if(head2==null){            return head1;        }        Node head;        if(head1.value<head2.value){            head = head1;            head.next = mergeList2(head1.next,head2);        }        else{            head = head2;            head.next = mergeList2(head1,head2.next);        }        return head;    }    public static void main(String[] args){        Node head1 = new Node(2);        head1.next = new Node(8);        head1.next.next = new Node(10);        head1.next.next.next = new Node(20);        Node head2= new Node(1);        head2.next = new Node(3);        head2.next.next = new Node(7);        head2.next.next.next = new Node(18);        Solution17 s17 = new Solution17();        Node new_head = s17.mergeList1(head1,head2);        while (new_head!=null){            System.out.format("   %d",new_head.value);            new_head = new_head.next;        }    }}