/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
public class BSTIterator {
Stack<TreeNode> stack=null;
public BSTIterator(TreeNode root) {
stack=new Stack<TreeNode>();
while(root!=null)
{
stack.push(root);
root=root.left;
}
}
/** @return whether we have a next smallest number */
public boolean hasNext() {
return !stack.isEmpty();
}
/** @return the next smallest number */
public int next() {
int res=0;
if(!stack.isEmpty())
{
TreeNode node=stack.pop();
res=node.val;
node=node.right;
while(node!=null)
{
stack.push(node);
node=node.left;
}
}
return res;
}
}
/**
* Your BSTIterator will be called like this:
* BSTIterator i = new BSTIterator(root);
* while (i.hasNext()) v[f()] = i.next();
*/
