Odd Even Linked List.cpp

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode* oddEvenList(ListNode* head) {
        if(!head || !head->next)return head;
        ListNode* oHead = head, *eHead = head->next, *oCurr = oHead, *eCurr = eHead;
        while(eCurr->next)
        {
            oCurr->next = eCurr->next;
            oCurr = oCurr->next;
            if(!oCurr->next)break;
            eCurr->next = oCurr->next;
            eCurr = eCurr->next;
        }
        if(eCurr->next)eCurr->next = nullptr;
        if(oCurr->next)oCurr->next = nullptr;
        oCurr->next = eHead;
        return oHead;
    }
};