Unidirectional linked list inversion
First create a one-way linked list
/**
*Unidirectional linked list * * / class node{
public Node(int value){
this.value = value;
}
public int value;
public Node next;
}- Head insertion
The head insertion method uses the double pointer method for head insertion
/**
*Method 1 * @ param head
* @return
*/
public static Node reverse1(Node head){
/**
*Judge whether the current node is empty or has only one node
*/
if (head == null || head.next == null) {
return head;
}
//Record the node of the last cur
Node pre = null;
//Record the next node of the current node
Node post;
while (head!=null){
//Move the post node forward
post = head.next;
//The next node of the current node points to the previous current node
head.next = pre;
//Assign the current node to pre for next use
pre = head;
//Move the current node forward
head = post;
}
//Since head = post has been moved forward in the last loop, pre is taken here as the inverted linked list
return pre;
}- Recursive inversion
/**
*Method 2, recursive * @ param head
* @return
*/
public static Node reverse2(Node head){
/**
*Judge whether the current node is empty or has only one node
*/
if (head == null || head.next == null) {
return head;
}
/**
*Get the next node recursively, and the node returned at the bottom is the tail of the linked list
*/
Node node = reverse2(head.next);
/**
*Reverse here
*/
head.next.next = head;
head.next = null;
return node;
}