Leetcode Recover Binary Search Tree

Elements of a binary search tree (BST) is swapped by mistake.

Recover the tree without changing its structure.

Note:
A solution using O (n) space is pretty straight forward. Could you devise a constant space solution?

Confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

1 /**2 * Definition for binary tree3 * public class TreeNode {4 * int val;5 * TreeNode left;6 * TreeNode right;7 * TreeNode (int x) {val = x;}8  * }9  */Ten  Public classSolution { One  A  -TreeNode N1 =NULL; -TreeNode N2 =NULL; theTreeNode pre =NULL; -  -      Public voidrecovertree (TreeNode root) { - findnodes (root); +         if(N1! =NULL&& N2! =NULL) { -             inttemp =N1.val; +N1.val =N2.val; AN2.val =temp; at         } -     } -  -     voidfindnodes (TreeNode root) { -         if(Root = =NULL) { -             return; in         } - findnodes (root.left); to         if(Pre! =NULL&& pre.val >root.val) { +             if(N1 = =NULL) { -N1 =Pre; the             } *N2 =Root; $         }Panax NotoginsengPre =Root; - findnodes (root.right); the     } +  A  the}

Leetcode Recover Binary Search Tree