class MaxStack {
TreeMap> map;
DoubleLinkedList dll;
public MaxStack() {
map = new TreeMap();
dll = new DoubleLinkedList();
}
public void push(int x) {
Node node = dll.add(x);
if(!map.containsKey(x))
map.put(x, new ArrayList());
map.get(x).add(node);
}
public int pop() {
int val = dll.pop();
List L = map.get(val);
L.remove(L.size() - 1);
if (L.isEmpty()) map.remove(val);
return val;
}
public int top() {
return dll.peek();
}
public int peekMax() {
return map.lastKey();
}
public int popMax() {
int max = peekMax();
List L = map.get(max);
Node node = L.remove(L.size() - 1);
dll.unlink(node);
if (L.isEmpty()) map.remove(max);
return max;
}
}
class DoubleLinkedList {
Node head, tail;
public DoubleLinkedList() {
head = new Node(0);
tail = new Node(0);
head.next = tail;
tail.prev = head;
}
public Node add(int val) {
Node x = new Node(val);
x.next = tail;
x.prev = tail.prev;
tail.prev = tail.prev.next = x;
return x;
}
public int pop() {
return unlink(tail.prev).val;
}
public int peek() {
return tail.prev.val;
}
public Node unlink(Node node) {
node.prev.next = node.next;
node.next.prev = node.prev;
return node;
}
}
class Node {
int val;
Node prev, next;
public Node(int v) {val = v;}
}