156: Binary Tree Upside Down

Given a binary tree where all the right nodes are either leaf nodes with a sibling (a left node that shares the same parent node) or empty, flip it upside down and turn it into a tree where the original right nodes turned into left leaf nodes. Return the new root.

For example:

Given a binary tree {1,2,3,4,5},

   1
  / \
 2   3
/ \
4 5

return the root of the binary tree [4,5,2,#,#,3,1].

 4
/ \
5  2
  / \
 3   1

http://blog.csdn.net/whuwangyi/article/details/43186045

 public TreeNode UpsideDownBinaryTree(TreeNode root) {
        TreeNode node = root, parent = null, right = null;
        while (node != null) {
            TreeNode left = node.left;
            node.left = right;
            right = node.right;
            node.right = parent;
            parent = node;
            node = left;
        }
        return parent;
 }

public TreeNode UpsideDownBinaryTree(TreeNode root) {
        TreeNode node = root, parent = null, right = null;
        while (node != null) {
            TreeNode left = node.left;
            node.left = right;
            right = node.right;
            node.right = parent;
            parent = node;
            node = left;
        }
        return parent;
}