[LeetCode] 230 - Kth Smallest Element in a BST

題意

在 Binary Search Tree 中找到第 K 小的元素。

解法

Inorder Traversal 後輸出第 K 個元素即可。

程式

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {number} k
 * @return {number}
 */
var kthSmallest = function(root, k) {
    
  let stack = [];
  let result = [];
  let node = root;
  
  while( stack.length !== 0 || node !== null ){
    while ( node !== null ){
      stack.push(node);
      node = node.left;
    }
    node = stack.pop();
    result.push(node.val);
    node = node.right;
  }
  return result[k-1];
};