剑指offer 删除链表中重复的结点（C++）（实现函数的模块化设计）

题目描述

在一个排序的链表中，存在重复的结点，请删除该链表中重复的结点，重复的结点不保留，返回链表头指针。 例如，链表1->2->3->3->4->4->5 处理后为 1->2->5

解题思路

1. 链表头指针判空。
2. 将链表中的元素复制到vector中。
3. 清空链表，保留头指针。
4. 删除vector中所有重复的元素。
5. 尾插法重新将vector中的元素赋值到链表中。

代码实现

/*
struct ListNode {
    int val;
    struct ListNode *next;
    ListNode(int x) :
        val(x), next(NULL) {
    }
};
*/
class Solution {
public:
    ListNode* deleteDuplication(ListNode* pHead)
    {
        if(pHead == NULL)
            return NULL;
        vector<int> ivec;
        ivec = CopyFromLinkListToVector(pHead);
        
        FreeLinkList(pHead);

        DeleteAllDuplication(ivec);
        
        InsertLinkListRear(pHead, ivec);

        return pHead;
    }
    
    vector<int> CopyFromLinkListToVector(ListNode* &pHead)
    {
        vector<int> ivec;
        if(pHead == NULL)
            return {};
        ListNode *p = pHead;
        for(; p; p = p->next)
            ivec.push_back(p->val);
        return ivec;
    }
    
    void FreeLinkList(ListNode* &pHead)
    {
        free(pHead);
        pHead = NULL;
        return;
    }
    
    void DeleteAllDuplication(vector<int> &ivec)
    {
        if(ivec.empty())
            return;
        vector<int>::iterator iter = ivec.begin();
        int flag = 0;
        while (iter != ivec.end())
        {    // 1 2 3 3 4 4 5
            flag = count(iter, ivec.end(), *iter);
            if (flag > 1)
                while (flag--)
                    iter = ivec.erase(iter);    
            else
                iter++;
        }
        return;
    }
    
    void InsertLinkListRear(ListNode* &pHead, vector<int> &ivec)
    {
        if(ivec.empty())
            return;
        ListNode* p = NULL, *temp = pHead;
        vector<int>::iterator iter = ivec.begin();
        while(iter != ivec.end())
        {
            p = new ListNode(*iter++);
            if(pHead)
            {
                temp->next = p;
                temp = p;
            }
            else
            {
                pHead = p;
                temp = p;
            }
                
        }
    }
};

VS2013上的实现：

#include<iostream>
#include<vector>
#include<algorithm> 
// 1 2 3 3 4 4 5

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

ListNode* CreateLinkList()
{
  ListNode* pHead = new ListNode(1);
  ListNode* p1 = new ListNode(2);
  pHead->next = p1;
  ListNode* p2 = new ListNode(3);
  p1->next = p2;
  ListNode* p3 = new ListNode(3);
  p2->next = p3;
  ListNode* p4 = new ListNode(4);
  p3->next = p4;
  ListNode* p5 = new ListNode(5);
  p4->next = p5;
  ListNode* p6 = new ListNode(5);
  p5->next = p6;
  return pHead;
}

vector<int> CopyFromLinkListToVector(ListNode* &pHead)
{
  vector<int> ivec;
  if (pHead == NULL)
    return{};
  ListNode *p = pHead;
  for (; p; p = p->next)
    ivec.push_back(p->val);
  return ivec;
}

void FreeLinkList(ListNode* &pHead)
{
  free(pHead);
  pHead = NULL;
  return;
}

void DeleteAllDuplication(vector<int> &ivec)
{
  if (ivec.empty())
    return;
  vector<int>::iterator iter = ivec.begin();
  int flag = 0;
  while (iter != ivec.end())
  {    // 1 2 3 3 4 4 5
    flag = count(iter, ivec.end(), *iter);
    if (flag > 1)
    while (flag--)
      iter = ivec.erase(iter);
    else
      iter++;
  }
  return;
}

void InsertLinkListRear(ListNode* &pHead, vector<int> &ivec)
{
  if (ivec.empty())
    return;
  ListNode* p = NULL, *temp = pHead;
  vector<int>::iterator iter = ivec.begin();
  while (iter != ivec.end())
  {
    p = new ListNode(*iter++);
    if (pHead)
    {
      temp->next = p;
      temp = p;
    }
    else
    {
      pHead = p;
      temp = p;
    }
  }
}

ListNode* deleteDuplication(ListNode* pHead)
{
  if (pHead == NULL)
    return NULL;
  vector<int> ivec;
  ivec = CopyFromLinkListToVector(pHead);

  FreeLinkList(pHead);

  DeleteAllDuplication(ivec);

  InsertLinkListRear(pHead, ivec);

  return pHead;
}

void PrintLinkList(ListNode* pHead)
{
  if (pHead == NULL)
    return;
  ListNode* p = pHead;
  for (; p; p = p->next)
  {
    cout << p->val << " ";
  }
  cout << endl;
}

void main()
{
  ListNode* pHead = CreateLinkList();
  PrintLinkList(pHead);
  deleteDuplication(pHead);
  cout << "整理之后：" << endl;
  PrintLinkList(pHead);
  system("pause");
  return;
}

运行截图：
1 2 3 3 4 5 5
整理之后：
2 4
请按任意键继续. . .