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-rw-r--r--src/org/traccar/helper/LocationTree.java116
1 files changed, 116 insertions, 0 deletions
diff --git a/src/org/traccar/helper/LocationTree.java b/src/org/traccar/helper/LocationTree.java
new file mode 100644
index 000000000..1d7d8ab25
--- /dev/null
+++ b/src/org/traccar/helper/LocationTree.java
@@ -0,0 +1,116 @@
+/*
+ * Copyright 2016 Anton Tananaev (anton.tananaev@gmail.com)
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.traccar.helper;
+
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+
+public class LocationTree {
+
+ public static class Item {
+
+ private Item left, right;
+ private float x, y;
+ private String data;
+
+ public Item(float x, float y) {
+ this(x, y, null);
+ }
+
+ public Item(float x, float y, String data) {
+ this.x = x;
+ this.y = y;
+ this.data = data;
+ }
+
+ public String getData() {
+ return data;
+ }
+
+ private float squaredDistance(Item item) {
+ return (x - item.x) * (x - item.x) + (y - item.y) * (y - item.y);
+ }
+
+ private float axisSquaredDistance(Item item, int axis) {
+ if (axis == 0) {
+ return (x - item.x) * (x - item.x);
+ } else {
+ return (y - item.y) * (y - item.y);
+ }
+ }
+
+ }
+
+ private Item root;
+
+ private ArrayList<Comparator<Item>> comparators = new ArrayList<>();
+
+ public LocationTree(List<Item> items) {
+ comparators.add(new Comparator<Item>() {
+ @Override
+ public int compare(Item o1, Item o2) {
+ return Float.compare(o1.x, o2.x);
+ }
+ });
+ comparators.add(new Comparator<Item>() {
+ @Override
+ public int compare(Item o1, Item o2) {
+ return Float.compare(o1.y, o2.y);
+ }
+ });
+ root = createTree(items, 0);
+ }
+
+ private Item createTree(List<Item> items, int depth) {
+ if (items.isEmpty()) {
+ return null;
+ }
+ Collections.sort(items, comparators.get(depth % 2));
+ int currentIndex = items.size() / 2;
+ Item median = items.get(currentIndex);
+ median.left = createTree(new ArrayList<>(items.subList(0, currentIndex)), depth + 1);
+ median.right = createTree(new ArrayList<>(items.subList(currentIndex + 1, items.size())), depth + 1);
+ return median;
+ }
+
+ public Item findNearest(Item search) {
+ return findNearest(root, search, 0);
+ }
+
+ private Item findNearest(Item current, Item search, int depth) {
+ int direction = comparators.get(depth % 2).compare(search, current);
+
+ Item next = (direction < 0) ? current.left : current.right;
+ Item other = (direction < 0) ? current.right : current.left;
+ Item best = (next == null) ? current : findNearest(next, search, depth + 1);
+ if (current.squaredDistance(search) < best.squaredDistance(search)) {
+ best = current;
+ }
+ if (other != null) {
+ if (current.axisSquaredDistance(search, depth % 2) < best.squaredDistance(search)) {
+ Item possibleBest = findNearest(other, search, depth + 1);
+ if (possibleBest.squaredDistance(search) < best.squaredDistance(search) ) {
+ best = possibleBest;
+ }
+ }
+ }
+
+ return best;
+ }
+
+}