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Binary Search Tree Iterator.java
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Binary Search Tree Iterator.java
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/**
* Definition for binary tree
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
import java.util.ArrayDeque;
public class BSTIterator {
private ArrayDeque<TreeNode> stack = new ArrayDeque<TreeNode>();
public BSTIterator(TreeNode root) {
TreeNode cur = root;
while(cur != null) {
stack.push(cur);
cur = cur.left;
}
}
/** @return whether we have a next smallest number */
public boolean hasNext() {
return stack.size() > 0;
}
/** @return the next smallest number */
public int next() {
TreeNode node = stack.pop();
int retval = node.val;
if(node.right != null) {
node = node.right;
while(node != null) {
stack.push(node);
node = node.left;
}
}
return retval;
}
}
/**
* Your BSTIterator will be called like this:
* BSTIterator i = new BSTIterator(root);
* while (i.hasNext()) v[f()] = i.next();
*/