99. Recover Binary Search Tree（js）

99. Recover Binary Search Tree

Two elements of a binary search tree (BST) are swapped by mistake.

Recover the tree without changing its structure.

Example 1:

Input: [1,3,null,null,2]

   1
  /
 3
  \
   2

Output: [3,1,null,null,2]

   3
  /
 1
  \
   2

Example 2:

Input: [3,1,4,null,null,2]

  3
 / \
1   4
   /
  2

Output: [2,1,4,null,null,3]

  2
 / \
1   4
   /
  3
题意：保持结构不变，纠正使其成为合法的二叉搜索树
代码如下：

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {void} Do not return anything, modify root in-place instead.
 */
var recoverTree = function(root) {
    let list=[];
    let vals=[];
    inorder(root,vals,list);
    vals.sort((a,b)=>a-b);
    for(let i=0;i<list.length;i++){
        list[i].val=vals[i];
    }
};
var inorder=function(root,vals,list){
    if(!root) return ;
    inorder(root.left,vals,list);
    list.push(root);
    vals.push(root.val);
    inorder(root.right,vals,list);
}