链表——移除链表

#include<iostream>
#include<list>
using namespace std;

struct ListNode {
    int val;  // 节点上存储的元素
    ListNode* next;  // 指向下一个节点的指针
    ListNode(int x) : val(x), next(NULL) {}  // 节点的构造函数
};

// 根据数组创建链表函数
ListNode* Arr2Chain(int a[], int num)
{
    // head point
    ListNode* head = NULL;  // newand malloc 两种方式申请内存
    //tail point
    ListNode* tail = NULL;
    ListNode* add = NULL;

    for (int i = 0; i < num; ++i) 
    {
        ListNode* add = new ListNode(a[i]);
        //    TreeNode *add= (TreeNode*)malloc(sizeof(TreeNode));
        //    headd->val =a[i];
        //    headd->next =NULL;
        if (tail != NULL)
        {
            tail->next = add;
            tail = add;
        }
        else 
        {
            head = tail = add;
        }

    }
    return head;
}

class Solution {
public:
    ListNode* removeElements(ListNode* head, int val)     // 链表移除函数
    {
        ListNode* dummyHead = new ListNode(0); // 设置一个虚拟头结点，并将其值初始化为0
        dummyHead->next = head; // 将虚拟头结点指向head，这样方便后面做删除操作
        ListNode* cur = dummyHead;
        while (cur->next != NULL) 
        {
            if (cur->next->val == val) 
            {
                ListNode* tmp = cur->next;
                cur->next = cur->next->next;
                delete tmp;
            }
            else 
            {
                cur = cur->next;
            }
        }
        head = dummyHead->next;
        delete dummyHead;
        return head;
    }
};


int main() {
    int a[] = { 0,1,2,3,4,5,6,7,8,9,2,3,2 };
    int num = sizeof(a) / sizeof(a[0]);

    ListNode* head = Arr2Chain(a, num);

    Solution s;
    ListNode* m_head = s.removeElements(head, 2);
    
    while (m_head != NULL)
    {
        cout << m_head->val << "  ";
        m_head = m_head->next;
    }
    return 0;
}