algorithm/Week_01/id_108/LeetCode_24_108.java at master · feixiangcode/algorithm · GitHub

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/**

* @author zhangruihao.zhang

* @version v1.0.0

* @since 2019/04/20

public class LeetCode_24_108 {

/**

* Definition for singly-linked list.

* public class ListNode {

* int val;

* ListNode next;

* ListNode(int x) { val = x; }

* }

class Solution1 {

public ListNode swapPairs(ListNode head) {

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

return head;

}

//标识要交换的第一个节点

ListNode first = head;

//标识要交换的第二个节点

ListNode second = head.next;

//标识下一组要交换的节点对

ListNode cur = second.next;

//交换

first.next = cur;

second.next = first;

head = second;

ListNode pre = first;

//下一组

first = cur;

second = cur == null || cur.next == null ? null : cur.next;

cur = second == null ? null : second.next;

while(first != null && second != null){

//交换

first.next = cur;

second.next = first;

pre.next = second;

pre = first;

//下一组

first = cur;

second = cur == null || cur.next == null ? null : cur.next;

cur = second == null ? null : second.next;

}

return head;

}

class Solution2 {

public ListNode swapPairs(ListNode head) {

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

return head;

}

//标识要交换的第一个节点

ListNode first = head;

//标识要交换的第二个节点

ListNode second = head.next;

//标识下一组要交换的节点对

ListNode cur = second.next;

//初始化前节点

ListNode pre = null ;

//第一次交换

first.next = cur;

second.next = first;

head = second;

while(true){

pre = first;

first = cur;

second = cur == null || cur.next == null ? null : cur.next;

cur = second == null ? null : second.next;

if(first == null || second == null){

break;

}

swap(pre,first,second,cur);

}

return head;

}

private void swap(ListNode pre,ListNode first,ListNode second,ListNode cur){

//交换

first.next = cur;

second.next = first;

pre.next = second;

}

algorithm/Week_01/id_108/LeetCode_24_108.java at master · feixiangcode/algorithm · GitHub

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