099 Recover Binary Search Tree 复原二叉搜索树

二叉排序树中有两个节点被交换了，要求把树恢复成二叉排序树。

详见：https://leetcode.com/problems/recover-binary-search-tree/submissions/

Java实现：

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public void recoverTree(TreeNode root) {
        List<TreeNode> node=new ArrayList<TreeNode>();
        List<Integer> val=new ArrayList<Integer>();
        inOrder(root,node,val);
        Collections.sort(val);
        for(int i=0;i<node.size();++i){
            if(node.get(i).val!=val.get(i)){
                node.get(i).val=val.get(i);
            }
        }
    }
    private void inOrder(TreeNode root,List<TreeNode> node,List<Integer> val){
        if(root==null){
            return;
        }
        inOrder(root.left,node,val);
        node.add(root);
        val.add(root.val);
        inOrder(root.right,node,val);
    }
}