173.二叉搜索树迭代器

2020-05-29

二叉搜索树迭代器

实现一个二叉搜索树迭代器。你将使用二叉搜索树的根节点初始化迭代器。

调用 next() 将返回二叉搜索树中的下一个最小的数。

题解:

思路1：二叉树的中序遍历

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 */
var BSTIterator = function (root) {
  this.arr = [];
  this.index = 0;
  let handler = (node) => {
    if(!node) return;
    handler(node.left);
    this.arr.push(node.val);
    handler(node.right);
  }
  handler(root);
};

/**
 * @return the next smallest number
 * @return {number}
 */
BSTIterator.prototype.next = function () {
  return this.arr[this.index++];
};

/**
 * @return whether we have a next smallest number
 * @return {boolean}
 */
BSTIterator.prototype.hasNext = function () {
  return this.index <= this.arr.length;
};

/**
 * 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()
 */