private void inOrder(TreeNode curr, Wrap w) {
if (curr == null) return;
inOrder(curr.left, w);
if (w.prev != null && w.prev.val > curr.val) {
if (first == null) {
first = w.prev;
}
second = curr;
}
w.prev = curr;
inOrder(curr.right, w);
}
public void recoverTree(TreeNode root) {
// Start typing your Java solution below
// DO NOT write main() function
first = null;
second = null;
// inOrder(root, null);
Wrap w = new Wrap();
w.prev = null;
inOrder(root, w);
int tmp = first.val;
first.val = second.val;
second.val = tmp;
}
