Differential Privacy Location Protection Scheme Based on Hilbert Curve

Algorithm 1

Spatial quadtree generation.

	Input: quad-tree root node , interest point set , quad-tree sub node-set , the number of levels of quad-tree
	Output: quad-tree index QT with location set
(1)	If
(2)	;
(3)	While do
(4)	For layer do
(5)	;//Create four new child nodes for the node on layer
(6)	;
(7)	End For
(8)	End While
(9)	Else
(10)	;//Create four new child nodes for the node on this layer
(11)	For each //For each interest point belonging to
(12)	If //If the interest point is stored in the region of the i-th child node of the quad-tree node
(13)	;//Move the interest points to their child nodes
(14)	End If
(15)	End For
(16)	//Mark the child node of interest pointas
(17)	; //Recursively callto insert the interest point into node
(18)	End If
(19)	Return