173. Binary Search Tree Iterator 

 1 public class BSTIterator {
 2     Queue<Integer> queue;
 3     public void build(TreeNode root){
 4         if(root == null) return;
 5         build(root.left);
 6         queue.offer(root.val);
 7         build(root.right);
 8         
 9     }
10 
11     public BSTIterator(TreeNode root) {
12         queue = new LinkedList<>();
13         build(root);
14         
15     }
16 
17     /** @return whether we have a next smallest number */
18     public boolean hasNext() {
19         return !queue.isEmpty();
20     }
21 
22     /** @return the next smallest number */
23     public int next() {
24         return queue.poll();
25     }
26 }
27 
28 /**
29  * Your BSTIterator will be called like this:
30  * BSTIterator i = new BSTIterator(root);
31  * while (i.hasNext()) v[f()] = i.next();
32  */

 

posted @ 2018-10-23 01:28  jasoncool1  阅读(86)  评论(0)    收藏  举报