Leetcode(链表题解)

Leetcode_206

反转链表

#include 
using namespace std;

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

ListNode* reverseList(ListNode* head)
{
    ListNode *pre = NULL;
    ListNode *cur = head;
    
    while(cur!=NULL)
    {
        ListNode *next = cur->next;
        cur ->next= pre ;
        pre = cur;
        cur = next;
        

    }
    return pre;
}

Leetcode_203

删除链表中指定的元素

#include 
using namespace std;

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

ListNode* removeElements(ListNode* head, int val)

{
    ListNode* temp = new ListNode(0);
    temp -> next = head;
    ListNode *cur = temp;
    while(cur!=NULL)
    {
        if(cur->next!=NULL&&cur->next->val==val)
        {
            ListNode *delnode = cur->next;
            cur -> next = delnode->next;
            delete delnode;
        }
        else
        {
            cur = cur->next;
        }
    }
    ListNode *retNode = temp->next;
    delete temp;
    return retNode;

}

Leetcode_24

链表元素两两交换

#include 
using namespace std;
struct ListNode
{
    int val;
    ListNode *next;
    ListNode(int x):val(x),next(NULL){}
    
};
ListNode* swapPairs(ListNode* head)
{
   ListNode *temp = new ListNode(0);
   temp->next = head;
   ListNode *p = temp;
   while(p->next && p->next->next)
   {
       ListNode *node1 = p->next;
       ListNode *node2 = node1->next;
       ListNode *next = node2->next;
       node2->next = node1;
       node1->next = next;
       p->next = node2;
       p = node1;
   }
   ListNode* retNode = temp->next;
   return retNode;
}

Leetcode_237

删除指定节点

void deleteNode(ListNode* node) {
    if(node==NULL)
        return;
    if(node->next == NULL)
        delete node;
    ListNode *delnode = node->next;
    node->val = delnode -> val;
    node ->next = delnode->next;
    delete delnode;

}