Create buildKDTree.m

Task/K-d-tree/Matlab/buildKDTree.m

@@ -0,0 +1,23 @@
+function node = buildKDTree(points, depth)
+    if nargin < 2
+        depth = 0;      % default depth to start building tree, otherwise specified in the function call
+    end
+    if isempty(points)
+        node = [];
+        return;
+    end
+
+    k = size(points, 2);        % Dimensionality of the points
+    axis = mod(depth, k) + 1;
+
+    % Sort point list and choose median as pivot element
+
+    sortedPoints = sortrows(points, axis);
+    medianIdx = floor(size(sortedPoints, 1) / 2) + 1;
+
+    % Create node and construct subtrees
+    
+    node = kdNode(sortedPoints(medianIdx, :), ...
+                  buildKDTree(sortedPoints(1 : medianIdx - 1, :), depth + 1), ...
+                  buildKDTree(sortedPoints(medianIdx + 1 : end, :), depth + 1));
+end