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| class Solution {
public ListNode swapPairs(ListNode head) {
if (head == null || head.next == null) {
return head;
}
Queue<ListNode> queue = new LinkedList<>();
ListNode p = head;
while (p.next != null) {
queue.add(p.next);
queue.add(p);
if (p.next.next == null) {
break;
} else if (p.next.next.next == null) {
queue.add(p.next.next);
break;
} else {
p = p.next.next;
}
}
ListNode ans = queue.poll();
p = ans;
while (!queue.isEmpty()) {
p.next = queue.poll();
p = p.next;
if (queue.size() == 0) {
p.next = null;
}
}
return ans;
}
}
|
