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Copy pathReverList.java
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60 lines (56 loc) · 1.84 KB
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package nowcoder;
import java.util.Stack;
public class ReverList {
public static class ListNode {
int val;
ListNode next = null;
}
public static void main(String []args) {
ListNode head=new ListNode();
head.val=1;
ListNode next1=new ListNode();
next1.val=2;
head.next=next1;
ListNode next2=new ListNode();
next2.val=3;
next1.next=next2;
ListNode result=ReverseList(head);
while(result!=null){
System.out.print(result.val + " ");
result=result.next;
}
}
public static ListNode ReverseList(ListNode head) {
Stack<ListNode> stack=new Stack();
if(head==null) return null;
while(head!=null){
stack.push(head);
head=head.next;
}
ListNode newHead,resultHead;
newHead=stack.pop();
System.out.print(newHead.val+" ");
resultHead=newHead;
System.out.print(newHead.val+" ");
while(!stack.isEmpty()){
newHead.next=stack.pop();
newHead=newHead.next;
// System.out.print(newHead.val+" ");
}
//newHead.next=null;
return null;
// return resultHead;
}
public static ListNode reverseListIterative(ListNode head) {
ListNode prev = null; //前指针节点
ListNode curr = head; //当前指针节点
//每次循环，都将当前节点指向它前面的节点，然后当前节点和前节点后移
while (curr != null) {
ListNode nextTemp = curr.next; //临时节点，暂存当前节点的下一节点，用于后移
curr.next = prev; //将当前节点指向它前面的节点
prev = curr; //前指针后移
curr = nextTemp; //当前指针后移
}
return prev;
}
}