problems/draft1.cpp at main · eeoeqaq/problems · GitHub

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#include<iostream>
struct ListNode {
    int val;
    ListNode *next;
    ListNode() : val(0), next(nullptr) {}
    ListNode(int x) : val(x), next(nullptr) {}
    ListNode(int x, ListNode *next) : val(x), next(next) {}
};

class Solution {
public:
    static ListNode* middleNode(ListNode* head) {
        ListNode* l1=head;
        ListNode* l2=head;
        int cnt=0;
        while(l2!=nullptr){
            l2=l2->next;
            if(cnt!=0&&cnt%2==0)l1=l1->next;
            cnt++;
        }
        return l1;
    }
    static ListNode* reverseList(ListNode* head) {
        ListNode* l1=nullptr;
        ListNode* l2=head;
        ListNode* l3;
        if(head!=nullptr)l3=head->next;
        while(l2!=nullptr){
            l2->next=l1;
            l1=l2;
            l2=l3;
            if(l3!=nullptr)l3=l3->next;
        }
        return l1;
    }
    static void reorderList(ListNode* head) {
        ListNode* mid = middleNode(head);
        ListNode* tar = head;
        ListNode* reversedBack = reverseList(mid);
        while(tar!=nullptr && reversedBack!=nullptr){
            ListNode* headBf=tar->next;
            ListNode* tailBf=reversedBack->next;
            tar->next=reversedBack;
            reversedBack->next=headBf;
            tar=headBf;
            reversedBack=tailBf;
        }
    }
};
int main(){
    ListNode* a=new ListNode(1,new ListNode(2,new ListNode(3,new ListNode(4,new ListNode(5)))));
    Solution::reorderList(a);
    while(a!=nullptr){
        std::cout<<a->val<<' ';
        a=a->next;
    }
}