从尾到头打印链表

Bertha 。 2023-06-21 07:20 129阅读 0赞

#### 输入一个链表，按链表从尾到头的顺序返回一个ArrayList。 ####

//方式一：
     public ArrayList<Integer> printListFromTailToHead(ListNode listNode) { 
            Stack<Integer> stack = new Stack();
            while (listNode != null){ 
                stack.push(listNode.val);
                listNode = listNode.next;
            }
    
            ArrayList<Integer> list = new ArrayList();
            while (!stack.isEmpty()){ 
                list.add(stack.pop());
            }
    
            return list;
        }
    
        @Test
        public void test() { 
            ListNode listNode = new ListNode();
            int arr[] ={ 1,22,333,4444,55555};
            ListNode next = listNode;
            for (int i :arr){ 
                next.setVal(i);
                if(i != 55555){ 
                    next.setNext(new ListNode());
                    next = next.getNext();
                }
            }
            Solution solution = new Solution();
            ArrayList<Integer> arrayList = solution.printListFromTailToHead(listNode);
            for(Integer i: arrayList){ 
                System.out.print(i+"\t");
            }
        }
    }
    
    //方式二：利用递归
    class Solution1 { 
        ArrayList<Integer> arrayList=new ArrayList<>();
        public ArrayList<Integer> printListFromTailToHead(ListNode listNode) { 
            if(listNode!=null){ 
                this.printListFromTailToHead(listNode.next);
                arrayList.add(listNode.val);
            }
            return arrayList;
        }
    }
    
    
    class ListNode { 
        int val;
        ListNode next = null;
    
         public ListNode getNext() { 
             return next;
         }
    
         public void setNext(ListNode next) { 
             this.next = next;
         }
    
         public void setVal(int val) { 
             this.val = val;
         }
    
     }