/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public void recoverTree(TreeNode root) {
        ArrayList<Integer> outOfPlace = new ArrayList<>();

        find(root, outOfPlace, Integer.MIN_VALUE, Integer.MAX_VALUE);
        if (outOfPlace.size() == 1) outOfPlace.add(root.val);

        swap(root, outOfPlace.get(0), outOfPlace.get(1));
    }

    private Integer find(TreeNode node, ArrayList<Integer> outOfPlace, int min, int max) {
        if (node == null) return null;

        if (node.val < min || node.val > max) return node.val;

        find(node.left, outOfPlace, min, node.val);
        find(node.right, outOfPlace, node.val, max);
    }

    private void swap(TreeNode node, int a, int b) {
        if (node == null) return;

        if (node.val == a) node.val = b;
        if (node.val == b) node.val = a;

        swap(node.left, a, b);
        swap(node.right, a, b);
    }
}