K-d Tree in TripAdvisor

Today, TripAdvisor held a tech talk in Columbia University. The topic is on k-d tree implemented in TripAdvisor to efficiently search MASSIVE location Tree.

Problem

Millions of locations, it ' s tough to perform Nearest Neighbor Search.

Solution

Using k-d tree to implement the location tree.

It ' s a space-partitioning balanced binary tree. and K is the number of dimension.

K-d Tree

Pseudocode

function Kdtree (List of points pointlist, int depth) {    //Select axis based on depth so the axis cycles through all V Alid values    var int axis: = depth mod k;            Sort point list and choose Median as pivot element    Select median by axis from Pointlist;            Create node and construct subtrees    var tree_node node;    Node.location: = median;    Node.leftchild: = Kdtree (points in pointlist before median, depth+1);    Node.rightchild: = Kdtree (points in pointlist after median, depth+1);    return node;}

K-d Tree in TripAdvisor