二叉搜索树向链表转换

    输入一棵二叉搜索树，将该二叉搜索树转换成一个排序的双向链表。要求不能创建任何新的结点，只能调整树中结点指针的指向。

   （本质就是二叉树的中序遍历算法）

   

/**
public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;

    public TreeNode(int val) {
        this.val = val;

    }

}
*/
public class Solution {
    private TreeNode header=null;
    
    private TreeNode pLastNode=null;
    
    public TreeNode Convert(TreeNode pRootOfTree) {
        if(pRootOfTree==null) return null;
        
        if(pRootOfTree.left==null && pRootOfTree.right==null) return pRootOfTree;
        
        convertToList(pRootOfTree);
        return header;
    }
    
    public void convertToList(TreeNode pRootOfTree){
        
        if(pRootOfTree.left!=null)
            convertToList(pRootOfTree.left);
        if(header==null){
            header=pRootOfTree;
            pLastNode=pRootOfTree;
        }else{
            pLastNode.right=pRootOfTree;
            pRootOfTree.left=pLastNode;
            pLastNode=pRootOfTree;
        }
        
        if(pRootOfTree.right!=null)
            convertToList(pRootOfTree.right);
    }
}