/*
 *@program: algStudy
 *@description: 链表节点
 *@author: chensy
 *@create: 2019-07-12 20:59
 */
class ListNode
{
     public int data;
     public ListNode next;
     public ListNode(int data){this.data = data;}

     /*
      * @Author chensy
      * @Description //TODO 删除最后一个节点
      * @Date 23:17 2019/7/12
      * @Param [first]
      * @return ListNode
      **/
     public static ListNode deleteLastNode(ListNode head) {

          if(head == null || head.next == null)
          {
               return head;
          }
          ListNode tmpNode = new ListNode(-1);
          tmpNode.next = head;

          while(head.next.next != null)
          {
               head = head.next;
          }

          head.next = null;

          return tmpNode.next;
     }

     /*
      * @Author chensy
      * @Description //TODO 删除指定索引节点, 索引从0开始
      * @Date 23:17 2019/7/12
      * @Param [node, index]
      * @return ListNode
      **/
     public static ListNode delete(ListNode head, int index) {

          if(head == null)
          {
               return null;
          }

          ListNode tmpNode = new ListNode(-1);
          tmpNode.next = head;


          int count = 1;
          while (head.next != null)
          {
               if(count++ == index)
               {
                    head.next = head.next.next;
               }

               //假若删除项在最后一项
               if(head.next == null)
               {
                    break;
               }

               head = head.next;
          }

          return tmpNode.next;

     }

     /*
      * @Author chensy
      * @Description //TODO 查找item是否存在该链表
      * @Date 23:18 2019/7/12
      * @Param [head, item]
      * @return boolean
      **/
     public static boolean find(ListNode head, int item) {
          if(head == null || (head.next == null && head.data != item))
          {
               return false;
          }

          while ( head.next != null)
          {
               if(head.data == item)
               {
                    return true;
               }
               head = head.next;
          }

          return false;

     }

     /*
      * @Author chensy
      * @Description //TODO 删除node后续节点
      * @Date 23:18 2019/7/12
      * @Param [head, node]
      * @return ListNode
      **/
     public static ListNode removeAfter(ListNode head, ListNode node) {
          if(node == null || head == null || head.data == node.data)
          {
               return null;
          }

          ListNode tmpNode = new ListNode(-1);
          tmpNode.next = head;


          while (head.next != null)
          {
               if(head.data == node.data)
               {
                    head.next = null;
                    break;
               }

               head = head.next;
          }

          return tmpNode.next;
     }

     /*
      * @Author chensy
      * @Description //TODO  合并节点, 右合并到左
      * @Date 23:18 2019/7/12
      * @Param [left, right]
      * @return ListNode
      **/
     public static ListNode insertNode(ListNode left, ListNode right) {
          if(left == null && right == null)
          {
               return null;
          }
          if (left == null) {
               return right;
          }
          if(right == null)
          {
               return left;
          }
          ListNode tmpNode = new ListNode(-1);
          tmpNode.next = left;
          left.next = right;

          return tmpNode.next;
     }

     /*
      * @Author chensy
      * @Description //TODO 删除指定Key的所有节点
      * @Date 23:19 2019/7/12
      * @Param [node, key]
      * @return ListNode
      **/
     public static ListNode remove(ListNode node, int key) {
          if(node == null || (node.next == null && node.data == key))
          {
               return null;
          }

          ListNode tmpNode = new ListNode(-1);
          tmpNode.next = node;

          while(node != null && node.next != null)
          {
               if(node.next.data == key) {
                    node.next = node.next.next;
               }
               //防止删除的是倒数第二个
               if (node.next != null && node.next.data == key)
               {
                    node.next = null;
                    break;
               }

               node = node.next;

          }

          return tmpNode.next;
     }

     /*
      * @Author chensy
      * @Description //TODO 查找链表中的最大值, 若不存在返回0 (循环解法)
      * @Date 13:26 2019/7/13
      * @Param [head]
      * @return int
      **/
     public static int max (ListNode head) {
          if(head == null)
          {
               return 0;
          }

          int max = head.data;
          while (head != null)
          {
               if(head.data > max)
               {
                    max = head.data;
               }
               head = head.next;
          }

          return max;
     }

     /*
      * @Author chensy
      * @Description //TODO 查找链表中的最大值, 若不存在返回0 (递归解法)
      * @Date 13:33 2019/7/13
      * @Param [head]
      * @return int
      **/
     public static int max2(ListNode head) {
          if(head == null)
          {
               return 0;
          }
          return head.next == null ? head.data : max(head.next);
     }
}