lintcode-easy-Flatten Binary Tree to Linked List

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: a TreeNode, the root of the binary tree
     * @return: nothing
     */
    public void flatten(TreeNode root) {
        // write your code here
        if(root == null)
            return;
            
        if(root.left == null && root.right == null)
            return;
        
        if(root.left != null){
            flatten(root.left);
        }
        
        if(root.right != null){
            flatten(root.right);
        }
        
        TreeNode temp = root.right;
        
        if(root.left != null){
            root.right = root.left;
            root.left = null;
            TreeNode p = root;
            while(p.right != null)
                p = p.right;
        
        p.right = temp; 
        }
        
        
        
        return;
    }
}