solution using queue, 5ms


  • 0
    J

    '''
    public class BSTIterator {
    Queue<Integer> q;
    public BSTIterator(TreeNode root) {
    q = new LinkedList<>();
    helper(root, q);
    }
    private void helper(TreeNode node, Queue<Integer> q) {
    if (node==null) return;
    helper(node.left, q);
    q.add(node.val);
    helper(node.right, q);
    }

    /** @return whether we have a next smallest number */
    public boolean hasNext() {
        return !q.isEmpty();
    }
    
    /** @return the next smallest number */
    public int next() {
        return q.poll();
    }
    

    }
    '''


  • 0
    W

    @jyu332
    it should limited O(h) memory, but your solution was O(n)


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