[数据结构与算法]数据结构学习记录（栈）

class ListNode{
?? ?public int val;
?? ?public int min;
?? ?public ListNode next;

?? ?public ListNode(int val, int min, ListNode next) {
?? ??? ?this.val = val;
?? ??? ?this.min = min;
?? ??? ?this.next = next;
?? ?}
}

class MinStack {
?? ?private ListNode head;
?? ?
//压栈
?? ?public void push(int x){
?? ??? ?if(empty())
?? ??? ??? ?head = new ListNode(x,x,null);
?? ??? ?else
?? ??? ??? ?head = new ListNode(x, Math.min(x, head.min), head);
?? ?}

//出栈
?? ?public void pop(){
?? ??? ?if(empty())
?? ??? ??? ?cout<<"this stack is empty!\n"<<endl;
?? ??? ?else
?? ??? ??? ?head =head.next;
?? ?}

//求栈顶元素
?? ?public void top(){
?? ??? ?if(empty())
?? ??? ??? ?cout<<"this stack is empty!\n"<<endl;
?? ??? ?else
?? ??? ??? ?return head.val;
?? ?}

//获得最小元素
?? ?public void getmin(){
?? ??? ?if(empty())
?? ??? ??? ?cout<<"this stack is empty!\n"<<endl;
?? ??? ?else
?? ??? ??? ?return head.min;
?? ?}

//判断栈是否为空
?? ?public boolean empty(){
?? ??? ?return head == null;
?? ?}
}