二叉树转链表

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public void flatten(TreeNode root) {
        if(root == null) return;
        TreeNode cur = root;
        while(cur != null){
            if(cur.left != null){
                TreeNode p = cur.left;
                while(p.right != null) p = p.right; 
                p.right = cur.right;
                cur.right = cur.left;
                cur.left = null;
            }
            cur = cur.right;
        }
    }
}