algorithm/Week_01/id_124/LeetCode_24_124.java at master · feixiangcode/algorithm · GitHub

35 lines (31 loc) · 1000 Bytes

import common.ListNode;

public class SwapPairs {

public ListNode swapPairs(ListNode head) {

if (head == null || head.next == null) {

return head;

}

ListNode dummy = new ListNode(-1);

dummy.next = head;

ListNode cur = dummy;

while (cur.next != null && cur.next.next != null) {

ListNode next = cur.next;

ListNode nextNext = cur.next.next;

next.next = nextNext.next;

nextNext.next = next;

cur.next = nextNext;

cur = nextNext.next;

}

return dummy.next;

}

public static void main(String[] args) {

ListNode node1 = new ListNode(1);

ListNode node2 = new ListNode(2);

ListNode node3 = new ListNode(3);

ListNode node4 = new ListNode(4);

node1.next = node2;

node2.next = node3;

node3.next = node4;

SwapPairs swapPairs = new SwapPairs();

swapPairs.swapPairs(node1);

}

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