static public TreeNode buildTree(int[] inorder, int[] postorder) {

		 return buildTree(postorder, inorder, 0, postorder.length-1, 0, inorder.length-1);

    }

    static public TreeNode buildTree(int[] postorder, int[] inorder, int pBegin, int pEnd, int iBegin, int iEnd){

        if(pBegin>pEnd)

            return null;

        TreeNode root = new TreeNode(postorder[pEnd]);

        int i = iBegin;

        for(;i<iEnd;i++)

            if(inorder[i]==root.val)

                break;

        int lenLeft = i-iBegin;

        root.left = buildTree(postorder, inorder, pBegin, pBegin+lenLeft-1, iBegin, i-1);

        root.right = buildTree(postorder, inorder, pBegin+lenLeft, pEnd-1, i+1, iEnd);

        return root;

    }