Increasing Order Search Tree

Description

Given a binary search tree, rearrange the tree in in-order so that the leftmost node in the tree is now the root of the tree, and every node has no left child and only 1 right child.

Example 1:
Input: [5,3,6,2,4,null,8,1,null,null,null,7,9]
   5
  / \
3    6

/ \    

2   4    8
 /        / \
1        7   9
Output: [1,null,2,null,3,null,4,null,5,null,6,null,7,null,8,null,9]
1
  

   2
    

     3
      

       4
        

         5
          

           6
            

             7
              

               8
                

9  

 

Constraints:

• The number of nodes in the given tree will be between 1 and 100.
• Each node will have a unique integer value from 0 to 1000.

Solution(javascript)

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {TreeNode}
 */
const increasingBST = (root) => {
  const vals = []
  const aux = (node) => {
    if (!node) {
      return
    }
    if (node.left) {
      aux(node.left)
    }
    vals.push({ val: node.val, left: null, right: null })
    if (node.right) {
      aux(node.right)
    }
  }
  aux(root)
  for (let i = 0; i < vals.length - 1; i++) {
    vals[i].right = vals[i + 1]
  }
  return vals[0]
}