public void Push(int x) { if (head == null) { head = new Node_minStack(x, x, null); } else { head = new Node_minStack(x, Math.Min(x, head.min), head); } }
public void Pop() { head = head.next; }
public Node_minStack(int val, int min, Node_minStack next) { this.val = val; this.min = min; this.next = next; }