173. 二叉搜索树迭代器

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class BSTIterator:

    def __init__(self, root: TreeNode):
        def inorder(root):
            if root is None:
                return
            inorder(root.left)
            self.vals.append(root.val)
            inorder(root.right)

        self.cur = 0
        self.vals = []
        inorder(root)

    def next(self) -> int:
        res = self.vals[self.cur]
        self.cur += 1
        return res

    def hasNext(self) -> bool:
        return self.cur < len(self.vals)


# Your BSTIterator object will be instantiated and called as such:
# obj = BSTIterator(root)
# param_1 = obj.next()
# param_2 = obj.hasNext()

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class BSTIterator {

    private List<Integer> vals;
    private int next;

    public BSTIterator(TreeNode root) {
        next = 0;
        vals = new ArrayList<>();
        inorder(root);
    }

    public int next() {
        return vals.get(next++);
    }

    public boolean hasNext() {
        return next < vals.size();
    }

    private void inorder(TreeNode root) {
        if (root == null) {
            return;
        }
        inorder(root.left);
        vals.add(root.val);
        inorder(root.right);
    }
}

/**
 * Your BSTIterator object will be instantiated and called as such:
 * BSTIterator obj = new BSTIterator(root);
 * int param_1 = obj.next();
 * boolean param_2 = obj.hasNext();
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 */
var BSTIterator = function (root) {
    this.stk = [];
    this.cur = root;
}


/**
 * @return {number}
 */
BSTIterator.prototype.next = function () {
    while (this.cur) {
        this.stk.push(this.cur);
        this.cur = this.cur.left;
    }
    this.cur = this.stk.pop();
    let res = this.cur.val;
    this.cur = this.cur.right;
    return (res);
};

/**
 * @return {boolean}
 */
BSTIterator.prototype.hasNext = function () {
    if (this.stk.length === 0 && this.cur === null) return false;
    return true;
};

/**
 * Your BSTIterator object will be instantiated and called as such:
 * var obj = new BSTIterator(root)
 * var param_1 = obj.next()
 * var param_2 = obj.hasNext()
 */