Title Description
List print head from the tail, which adds it to the output ArrayList
Ideas analysis
- Recursive ideas
- Using the stack
Java code
public class Offer006 {
public static void main(String[] args) {
ListNode ListNode1 = new ListNode(1);
ListNode ListNode2 = new ListNode(2);
ListNode ListNode3 = new ListNode(9);
ListNode ListNode4 = new ListNode(6);
ListNode ListNode5 = new ListNode(99);
ListNode1.next = ListNode2;
ListNode2.next = ListNode3;
ListNode3.next = ListNode4;
ListNode4.next = ListNode5;
ArrayList<Integer> result = Offer006.printListFromTailToHead(ListNode1);
for (int i = 0; i < result.size(); i++) {
System.out.println(result.get(i));
}
}
public static ArrayList<Integer> printListFromTailToHead(ListNode listNode) {
return Solution3(listNode);
}
// =================******** 题 解 **************======================
// 此处要声明一个成员变量list用来存放 链表中的值
private static ArrayList<Integer> list = new ArrayList<Integer>();
/**
* 递归的方法
*
* @param listNode
* @return
*/
private static ArrayList<Integer> Solution1(ListNode listNode) {
if (listNode != null) {
Solution1(listNode.next);
list.add(listNode.val);
}
return list;
}
/**
* 利用栈，占中存放ListNode
*
* @param listNode
* @return
*/
private static ArrayList<Integer> Solution2(ListNode listNode) {
Stack<ListNode> stack = new Stack<ListNode>();
while (listNode != null) {
stack.push(listNode);
listNode = listNode.next;
}
while (!stack.isEmpty()) {
list.add(stack.pop().val);
}
return list;
}
/**
* 利用栈 栈中存放值
*
* @param listNode
* @return
*/
private static ArrayList<Integer> Solution3(ListNode listNode) {
Stack<Integer> stack = new Stack<Integer>();
while (listNode != null) {
stack.push(listNode.val);
listNode = listNode.next;
}
while (!stack.isEmpty()) {
list.add(stack.pop());
}
return list;
}
}