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;
    }
};