LeetCode: Swap pairs

swap_pairs.cpp

/*
 * In a competition to see who would use the least pointers
 * for reversing nodes in a linked list, I think this solution
 * should be entered. There are easier solutions to read/spot,
 * but I think this is the most elegant.
 */

class Solution {
public:
    ListNode *swapPairs(ListNode *head) {
        if (!head || !head->next) return head;
        
        ListNode newHead(0);
        newHead.next = head;
        ListNode *prev = &newHead;
        head=head->next;
        
        while (head) {
            prev->next->next = head->next;
            head->next = prev->next;
            prev->next = head;
            prev = head->next;
            head = (prev && prev->next) ? prev->next->next : NULL;
        }
        
        return newHead.next;
    }
}