解题思路：
morris遍历先中序把整棵树遍历一遍
提交代码：
class BSTIterator {
private List<Integer> nums=new ArrayList<Integer>();
private int p=0;
public BSTIterator(TreeNode root) {
TreeNode cur=root,tmp=root;
while(cur!=null) {
if(cur.left!=null) {
tmp=cur.left;
while(tmp.right!=null&&tmp.right!=cur)
tmp=tmp.right;
if(tmp.right==null) {
tmp.right=cur;
cur=cur.left;
}else {
nums.add(cur.val);
cur=cur.right;
}
}else {
nums.add(cur.val);
cur=cur.right;
}
}
}
/** @return the next smallest number */
public int next() {
return nums.get(p++);
}
/** @return whether we have a next smallest number */
public boolean hasNext() {
if(p<nums.size()) return true;
return false;
}
}