چهار درخت یک ساختار داده ای است که برای یافتن نقاط نزدیک به یک نقطه، با جستجو در یک منطقه اطراف نقطه مورد نظر مفید است.
با استفاده از چهاردرخت، میتوانید نقاطی را در محدوده دوبعدی جستجو کنید، جایی که آن نقاط به عنوان مختصات lat/lng یا مختصات دکارتی (x، y) تعریف میشوند. Quadtree سطل هایی از مختصات را در گره ها ذخیره می کند و آنها را بر اساس منطقه (جعبه مرزی) فهرست می کند. برای یافتن یک جفت مختصات معین، از گره های درخت چهارگانه عبور می کنید.
اضافه کردن یک چهار درخت و جستجو برای نقاط در یک منطقه مشخص
کد زیر یک چهار درخت ایجاد می کند، سپس تمام نقاط یک منطقه مشخص را جستجو می کند:
سویفت
importGoogleMapsUtilsclassQuadTreeItem:NSObject,GQTPointQuadTreeItem{privateletgqtPoint:GQTPointinit(point:GQTPoint){self.gqtPoint=point}funcpoint()->GQTPoint{returngqtPoint}/// Function demonstrating how to create and use a quadtreeprivatefunctest(){// Create a quadtree with bounds of [-2, -2] to [2, 2].letbounds=GQTBounds(minX:-2,minY:-2,maxX:2,maxY:2)guardlettree=GQTPointQuadTree(bounds:bounds)else{return}// Add 4 points to the tree.tree.add(QuadTreeItem(point:GQTPoint(x:-1,y:-1)))tree.add(QuadTreeItem(point:GQTPoint(x:-1,y:-1)))tree.add(QuadTreeItem(point:GQTPoint(x:-1,y:1)))tree.add(QuadTreeItem(point:GQTPoint(x:1,y:1)))tree.add(QuadTreeItem(point:GQTPoint(x:1,y:-1)))// Search for items within the rectangle with lower corner of (-1.5, -1.5)// and upper corner of (1.5, 1.5).letsearchBounds=GQTBounds(minX:-1.5,minY:-1.5,maxX:1.5,maxY:1.5)foritemintree.search(with:searchBounds)as![QuadTreeItem]{print("(\(item.point().x), \(item.point().y))");}}}
هدف-C
@importGoogleMapsUtils;@interfaceQuadTreeItem : NSObject<GQTPointQuadTreeItem>-(instancetype)initWithPoint:(GQTPoint)point;@end@implementationQuadTreeItem{GQTPoint_point;}-(instancetype)initWithPoint:(GQTPoint)point{if((self=[superinit])){_point=point;}returnself;}-(GQTPoint)point{return_point;}/// Function demonstrating how to create and use a quadtree-(void)test{// Create a quadtree with bounds of [-2, -2] to [2, 2].GQTBoundsbounds={-2,-2,2,2};GQTPointQuadTree*tree=[[GQTPointQuadTreealloc]initWithBounds:bounds];// Add 4 points to the tree.[treeadd:[[QuadTreeItemalloc]initWithPoint:(GQTPoint){-1,-1}]];[treeadd:[[QuadTreeItemalloc]initWithPoint:(GQTPoint){-1,1}]];[treeadd:[[QuadTreeItemalloc]initWithPoint:(GQTPoint){1,1}]];[treeadd:[[QuadTreeItemalloc]initWithPoint:(GQTPoint){1,-1}]];// Search for items within the rectangle with lower corner of (-1.5, -1.5)// and upper corner of (1.5, 1.5).NSArray*foundItems=[treesearchWithBounds:(GQTBounds){-1.5,-1.5,1.5,1.5}];for(QuadTreeItem*iteminfoundItems){NSLog(@"(%lf, %lf)",item.point.x,item.point.y);}}@end
تاریخ آخرین بهروزرسانی 2025-07-23 بهوقت ساعت هماهنگ جهانی.
[[["درک آسان","easyToUnderstand","thumb-up"],["مشکلم را برطرف کرد","solvedMyProblem","thumb-up"],["غیره","otherUp","thumb-up"]],[["اطلاعاتی که نیاز دارم وجود ندارد","missingTheInformationINeed","thumb-down"],["بیشازحد پیچیده/ مراحل بسیار زیاد","tooComplicatedTooManySteps","thumb-down"],["قدیمی","outOfDate","thumb-down"],["مشکل ترجمه","translationIssue","thumb-down"],["مشکل کد / نمونهها","samplesCodeIssue","thumb-down"],["غیره","otherDown","thumb-down"]],["تاریخ آخرین بهروزرسانی 2025-07-23 بهوقت ساعت هماهنگ جهانی."],[[["\u003cp\u003eThis page explains the quadtree utility within the Maps SDK for iOS Utility Library, a data structure for efficiently finding nearby points.\u003c/p\u003e\n"],["\u003cp\u003eQuadtrees enable searching for points within a 2D range using latitude/longitude or cartesian coordinates by indexing them by region.\u003c/p\u003e\n"],["\u003cp\u003eTo use the quadtree, you must first set up the Maps SDK for iOS Utility Library as a prerequisite.\u003c/p\u003e\n"],["\u003cp\u003eCode examples are provided to demonstrate creating a quadtree, adding points, and searching for points within a specified area in both Swift and Objective-C.\u003c/p\u003e\n"]]],[],null,["This page describes the quadtree utility that's available in the\n[utility library\nfor the Maps SDK for iOS](https://github.com/googlemaps/google-maps-ios-utils).\n\nA quadtree is a data structure that's useful for finding points near a single\npoint, by searching inside an area surrounding the point of interest.\n\nUsing a quadtree, you can search efficiently for points within a 2D range,\nwhere those points are defined as lat/lng coordinates or as cartesian (x, y)\ncoordinates. The quadtree stores buckets of coordinates in nodes, and indexes\nthem by region (bounding box). To find a given coordinate pair, you traverse\nthrough the nodes of the quadtree.\n\nPrerequisites and notes\n\nThe quadtree utility is part of the\n[Maps SDK for iOS\nUtility Library](https://github.com/googlemaps/google-maps-ios-utils). If you haven't yet set up the library,\nfollow the [setup guide](/maps/documentation/ios-sdk/utility/setup)\nbefore reading the rest of this page.\n\nAdding a quadtree and search for points in a given area\n\nThe following code creates a quadtree, then searches for all points within\na given area: \n\nSwift \n\n```swift\nimport GoogleMapsUtils\n\nclass QuadTreeItem : NSObject, GQTPointQuadTreeItem {\n private let gqtPoint : GQTPoint\n\n init(point : GQTPoint) {\n self.gqtPoint = point\n }\n\n func point() -\u003e GQTPoint {\n return gqtPoint\n }\n\n /// Function demonstrating how to create and use a quadtree\n private func test() {\n\n // Create a quadtree with bounds of [-2, -2] to [2, 2].\n let bounds = GQTBounds(minX: -2, minY: -2, maxX: 2, maxY: 2)\n guard let tree = GQTPointQuadTree(bounds: bounds) else {\n return\n }\n\n // Add 4 points to the tree.\n tree.add(QuadTreeItem(point: GQTPoint(x: -1, y: -1)))\n tree.add(QuadTreeItem(point: GQTPoint(x: -1, y: -1)))\n tree.add(QuadTreeItem(point: GQTPoint(x: -1, y: 1)))\n tree.add(QuadTreeItem(point: GQTPoint(x: 1, y: 1)))\n tree.add(QuadTreeItem(point: GQTPoint(x: 1, y: -1)))\n\n // Search for items within the rectangle with lower corner of (-1.5, -1.5)\n // and upper corner of (1.5, 1.5).\n let searchBounds = GQTBounds(minX: -1.5, minY: -1.5, maxX: 1.5, maxY: 1.5)\n for item in tree.search(with: searchBounds) as! [QuadTreeItem] {\n print(\"(\\(item.point().x), \\(item.point().y))\");\n }\n }\n}\n \n```\n\nObjective-C \n\n```objective-c\n@import GoogleMapsUtils;\n\n@interface QuadTreeItem : NSObject\u003cGQTPointQuadTreeItem\u003e\n- (instancetype)initWithPoint:(GQTPoint)point;\n@end\n\n@implementation QuadTreeItem {\n GQTPoint _point;\n}\n\n- (instancetype)initWithPoint:(GQTPoint)point {\n if ((self = [super init])) {\n _point = point;\n }\n return self;\n}\n\n- (GQTPoint)point {\n return _point;\n}\n\n/// Function demonstrating how to create and use a quadtree\n- (void)test {\n // Create a quadtree with bounds of [-2, -2] to [2, 2].\n GQTBounds bounds = {-2, -2, 2, 2};\n GQTPointQuadTree *tree = [[GQTPointQuadTree alloc] initWithBounds:bounds];\n\n // Add 4 points to the tree.\n [tree add:[[QuadTreeItem alloc] initWithPoint:(GQTPoint){-1, -1}]];\n [tree add:[[QuadTreeItem alloc] initWithPoint:(GQTPoint){-1, 1}]];\n [tree add:[[QuadTreeItem alloc] initWithPoint:(GQTPoint){1, 1}]];\n [tree add:[[QuadTreeItem alloc] initWithPoint:(GQTPoint){1, -1}]];\n\n // Search for items within the rectangle with lower corner of (-1.5, -1.5)\n // and upper corner of (1.5, 1.5).\n NSArray *foundItems = [tree searchWithBounds:(GQTBounds){-1.5, -1.5, 1.5, 1.5}];\n\n for (QuadTreeItem *item in foundItems) {\n NSLog(@\"(%lf, %lf)\", item.point.x, item.point.y);\n }\n}\n\n@end\n \n```"]]