leetcode链表--12、remove-duplicates-from-sorted-list-ii（删除排序链表中全部的重复结点）

题目描述

 

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

For example,

Given1->2->3->3->4->4->5, return1->2->5.

Given1->1->1->2->3, return2->3.

 

解题思路：

1）首先记录当前结点指向的值tmp

2）如果下一结点不等于该值，则将该结点连入返回的链表

3）若下一结点等于该值，则找到下一个不等于该值的结点

4）然后进行下次操作

5）p->next = NULL目的是断开p当前指向结点与head后不符合的结点断开

例如：1->2->2   此时phead->next = 1, p 指向的是1->2->2   且p指向1  p->next = NULL 就断开了不符合条件的2->2   此时phead 指向的链表只包含1

#include <iostream>
#include <malloc.h>
using namespace std;
struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

class Solution {
public:
    ListNode *deleteDuplicates(ListNode *head) {
        if(head == NULL)
            return NULL;
        ListNode *phead = new ListNode(0);
        ListNode *p = phead;
        while(head != NULL)
        {
            int tmp = head->val;
            if(head->next == NULL || head->next->val != tmp)
            {
                p->next = head;
                p = p->next;
                head = head->next;
            }
            else
            {
                while(head->next != NULL && head->next->val == tmp)
                {
                    head = head->next;
                }
                head = head->next;
            }
        }
        p->next = NULL;//断开p与head后面不符合要求的结点的联系
        return phead->next;
    }
};
ListNode *CreateList(int n)
{
    ListNode *head;
    ListNode *p,*pre;
    int i;
    head=(ListNode *)malloc(sizeof(ListNode));
    head->next=NULL;
    pre=head;
    for(i=1;i<=n;i++)
    {
        p=(ListNode *)malloc(sizeof(ListNode));
        cin>>p->val;
        pre->next=p;
        pre=p;
    }
    p->next=NULL;

    return head->next;
}
/*-------------------------输出链表-----------------------------------*/
void PrintList(ListNode *h)
{
    ListNode *p;

    p=h;//不带空的头结点
    while(p)
    {
        cout<<p->val<<" ";
        p=p->next;
        cout<<endl;
    }
}
int main()
{
    int n1;
    int x;
    ListNode *h1;
    cout<<"输入链表1的结点数目"<<endl;
    cin>>n1;
    h1 = CreateList(n1);
    cout<<"链表1为："<<endl;
    PrintList(h1);
    Solution s;
    h1 = s.deleteDuplicates(h1);
    cout<<"删除全部重复结点后链表1为："<<endl;
    PrintList(h1);
}