LeetCode_Remove Duplicates from Sorted List II

Given a sorted linked list, delete all nodes that have duplicate numbers, leaving only distinct numbers from the original list.



For example,

Given 1->2->3->3->4->4->5, return 1->2->5.

Given 1->1->1->2->3, return 2->3.

　　

/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     ListNode *next;

 *     ListNode(int x) : val(x), next(NULL) {}

 * };

 */

class Solution {

public:

         ListNode *deleteDuplicates(ListNode *head) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        if(head == NULL || head->next == NULL) return head;

        int curVal = head->val;

        // P指向已经处理的合法listNode 的最后一个Node

        //q 指向当前政要处理的节点

        ListNode *p = NULL,*q = head, *temp;

        head = NULL ;       

        bool needDelete = false ;

        while(q)

        {  

            if(needDelete == false){

                if(q->next && q->next->val == q->val){

                     curVal = q->val;

                     needDelete = true;

                     temp = q->next->next;

                     delete q->next;

                     delete q;

                     q = temp;

                }else{

                     if(head == NULL)

                     { 

                        head = q;

                        p = q;

                     }else{

                      p->next = q;

                      p = q;

                      }

                      q = q->next;

                }                

            }else{ // else of needDelete = true

            

                 if(q->val == curVal)

                 {

                    temp = q->next;

                    delete q;

                    q = temp;

                 }else{

                     needDelete =false;

                 }

            }

        }

        

        if(p)

            p->next = NULL;

        

        return head ;

    }

};

 重写： 加了个虚拟根节点，从然使得自己从边界中解放出来

/**

 * Definition for singly-linked list.

 * struct ListNode {

 *     int val;

 *     ListNode *next;

 *     ListNode(int x) : val(x), next(NULL) {}

 * };

 */

class Solution {

public:

    ListNode *deleteDuplicates(ListNode *head) {

        // Start typing your C/C++ solution below

        // DO NOT write int main() function

        if(head == NULL || head ->next == NULL) return head;

        

		ListNode * head0, *cur;

		head0 = new ListNode(0);

		head0->next = head;

		head = head0;

		cur = head0;

		

		while(cur->next != NULL){

			ListNode * p = cur->next;

			ListNode *temp;

			while(p->next != NULL && p->next->val == p->val)

			{

    			temp = p;

			    p = p->next;

			    delete temp;

			}

			if(p == cur->next){

				cur = cur->next;

			}else{

				cur->next = p->next; 

				delete p;

			}

		}

		

		

		return head->next;

    }

};