我已经为n个点实现了四叉树结构以及一种返回给定矩形内点数组的方法。但我似乎找不到一种有效地找到距离给定点最近的点的算法。我是否漏掉了一些明显的东西?我认为递归解决方案是正确的方法?
我使用Objective C编写代码,但伪代码也可以。此外,我实际上存储的是纬度和经度数据,点之间的距离沿着大圆弧线。
编辑:这是我的树插入和细分代码
接近但不完美!
我使用Objective C编写代码,但伪代码也可以。此外,我实际上存储的是纬度和经度数据,点之间的距离沿着大圆弧线。
编辑:这是我的树插入和细分代码
- (BOOL)insert:(id<PASQuadTreeDataPoint>)dataPoint {
BOOL pointAdded = false;
// If the point lies within the region
if(CGRectContainsPoint(self.region, dataPoint.point)) {
// If there are less than 4 points then add this point
if(self.dataPoints.count < kMaxPointsPerNode) {
[self.dataPoints addObject:dataPoint];
pointAdded = true;
}
else {
// Subdivide into 4 quadrants if not already subdivided
if(northEast == nil) [self subdivide];
// Attempt to add the point to one of the 4 subdivided quadrants
if([northEast insert:dataPoint]) return true;
if([southEast insert:dataPoint]) return true;
if([southWest insert:dataPoint]) return true;
if([northWest insert:dataPoint]) return true;
}
}
return pointAdded;
}
- (void)subdivide {
// Compute the half width and the origin
CGFloat width = self.region.size.width * 0.5f;
CGFloat height = self.region.size.height * 0.5f;
CGFloat x = self.region.origin.x;
CGFloat y = self.region.origin.y;
// Create a new child quadtree with the region divided into quarters
self.northEast = [PASQuadTree quadTreeWithRegion:CGRectMake(x + width, y, width, height)];
self.southEast = [PASQuadTree quadTreeWithRegion:CGRectMake(x + width, y + height, width, height)];
self.southWest = [PASQuadTree quadTreeWithRegion:CGRectMake(x, y + height, width, height)];
self.northWest = [PASQuadTree quadTreeWithRegion:CGRectMake(x, y, width, height)];
}
编辑: 我已经编写了以下代码来查找包含该点的最小节点(叶子):
-(PASQuadTree *)nodeThatWouldContainPoint:(CGPoint)point {
PASQuadTree *node = nil;
// If the point is within the region
if (CGRectContainsPoint(self.region, point)) {
// Set the node to this node
node = self;
// If the node has children
if (self.northEast != nil) {
// Recursively check each child to see if it would contain the point
PASQuadTree *childNode = [self.northEast nodeThatWouldContainPoint:point];
if (!childNode) childNode = [self.southEast nodeThatWouldContainPoint:point];
if (!childNode) childNode = [self.southWest nodeThatWouldContainPoint:point];
if (!childNode) childNode = [self.northWest nodeThatWouldContainPoint:point];
if (childNode) node = childNode;
}
}
return node;
}
接近但不完美!