Interschimbare

#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
class ListNode {
  	public:
 		ListNode* next;
  		int val;
  		ListNode() : val(0), next(nullptr) {}
  		ListNode(int val) : val(val), next(nullptr) {}
  		~ListNode() {
			if (next) {
				delete next;
			}
		}
};

ListNode* swapPairs(ListNode* head) {
	// TODO: implementati functia ce interschimba nodurile doua cate doua.
    ListNode* temp = head;
    ListNode* prev;
    ListNode* temp1;
    if (temp != NULL && temp->next != NULL) {
        temp1 = temp->next;
        temp->next = temp1->next;
        temp1->next = temp;
        prev = temp;
        temp = temp->next;
        head = temp1;
    }
    while (temp != NULL && temp->next != NULL) {
        temp1 = temp->next;
        temp->next = temp1->next;
        temp1->next = temp;
        prev->next = temp1;
        prev = temp;
        temp = temp->next;
    }
  	return head;
}

int main() {
  	int n;
  	// TODO: Form the list and call swapPairs
    cin >> n;
    int x;
    cin >> x;
    ListNode* res = new ListNode(x);
    ListNode* it = res;
    for (int i = 1; i < n; i++) {
        cin >> x;
        ListNode* tmp = new ListNode(x);
        it->next = tmp;
        it = tmp;
    }
    res = swapPairs(res);
  	for (int i = 0; i < n; ++i) {
		cout << res->val << " ";
      	res = res->next;
    }
}