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T126.java
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74 lines (66 loc) · 1.8 KB
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/**
* @Author:Aliyang
* @Data: Created in 下午10:38 18-6-16
* swap-nodes-in-pairs：我的解法
* 思路：同T125，更简单
**/
public class T126 {
public static class ListNode {
int val;
ListNode next;
ListNode(int x) {
val = x;
next = null;
}
}
public ListNode swapPairs(ListNode head) {
int len=0;
ListNode tmpHead=head;
while (tmpHead!=null){
len++;
tmpHead=tmpHead.next;
}
return reverse(head,len,2);
}
private ListNode reverse(ListNode head,int n,int k){
if (n<k)
return head;
ListNode tmpHead=head;
int count=0;
ListNode first=null;
ListNode pre=null;
while (count<=k){
if (count==0){
first=tmpHead;//记录每一次的第一个位置
pre=tmpHead;
tmpHead=tmpHead.next;
}else if (count<k){//反转
ListNode next=tmpHead.next;
tmpHead.next=pre;
pre=tmpHead;
tmpHead=next;
}else if (count==k){
first.next=reverse(tmpHead,n-k,k);//当前k个节点的第一个指向下层返回的头结点
first=tmpHead;
}
count++;
}
return pre;
}
public static void main(String[] args){
T126 t=new T126();
ListNode head=new ListNode(1);
ListNode realHead=head;
head.next=new ListNode(2);
head=head.next;
head.next=new ListNode(3);
head=head.next;
head.next=new ListNode(4);
head=head.next;
ListNode res=t.swapPairs(realHead);
while (res!=null){
System.out.print(res.val+",");
res=res.next;
}
}
}