/**public class TreeNode {    int val = 0;    TreeNode left = null;    TreeNode right = null;    public TreeNode(int val) {        this.val = val;    }}*/public class Solution {    public TreeNode Convert(TreeNode pRootOfTree) {        if(pRootOfTree==null){            return null;        }        if(pRootOfTree.left==null && pRootOfTree.right==null){            return pRootOfTree;        }        //左子树        TreeNode leftNode = Convert(pRootOfTree.left);//        TreeNode p = leftNode;        while(p!=null && p.right!=null ){            p = p.right;        }        if(leftNode!=null){            p.right = pRootOfTree;            pRootOfTree.left = p;        }                TreeNode rightNode = Convert(pRootOfTree.right);        if(rightNode!=null){            rightNode.left = pRootOfTree;            pRootOfTree.right = rightNode;        }                        leftNode=leftNode!=null?leftNode:pRootOfTree;        return leftNode;    }        }