下面是来自https://rosettacode.org/wiki/K-d_tree的KD树实现的python代码,代码如下:
from random import seed, random
from time import clock
from operator import itemgetter
from collections import namedtuple
from math import sqrt
from copy import deepcopy
def sqd(p1, p2):
return sum((c1 - c2) ** 2 for c1, c2 in zip(p1, p2))
class KdNode(object):
__slots__ = ("dom_elt", "split", "left", "right")
def __init__(self, dom_elt, split, left, right):
self.dom_elt = dom_elt
self.split = split
self.left = left
self.right = right
class Orthotope(object):
__slots__ = ("min", "max")
def __init__(self, mi, ma):
self.min, self.max = mi, ma
class KdTree(object):
__slots__ = ("n", "bounds")
def __init__(self, pts, bounds):
def nk2(split, exset):
if not exset:
return None
exset.sort(key=itemgetter(split))
print('-------------------------------')
print('set: ',exset, 'split: ',split)
m = len(exset) // 2
d = exset[m]
print('pivot point:', d, 'm: ',m)
while m + 1 < len(exset) and exset[m + 1][split] == d[split]:
m += 1
print('pivot point:', d, 'm: ',m)
s2 = (split + 1) % len(d) # cycle coordinates
return KdNode(d, split, nk2(s2, exset[:m]),
nk2(s2, exset[m + 1:]))
self.n = nk2(0, pts)
self.bounds = bounds
if __name__ == "__main__":
seed(1)
P = lambda *coords: list(coords)
kd1 = KdTree([P(2, 3), P(5, 4), P(9, 6), P(4, 7), P(8, 1), P(7, 2)],
Orthotope(P(0, 0), P(10, 10)))
结果如下:
-------------------------------
set: [[2, 3], [4, 7], [5, 4], [7, 1], [7, 2], [9, 6]] split: 0
pivot point: [7, 1] m: 3
pivot point: [7, 1] m: 4
-------------------------------
set: [[7, 1], [2, 3], [5, 4], [4, 7]] split: 1
pivot point: [5, 4] m: 2
pivot point: [5, 4] m: 2
-------------------------------
set: [[2, 3], [7, 1]] split: 0
pivot point: [7, 1] m: 1
pivot point: [7, 1] m: 1
-------------------------------
set: [[2, 3]] split: 1
pivot point: [2, 3] m: 0
pivot point: [2, 3] m: 0
-------------------------------
set: [[4, 7]] split: 0
pivot point: [4, 7] m: 0
pivot point: [4, 7] m: 0
-------------------------------
set: [[9, 6]] split: 1
pivot point: [9, 6] m: 0
pivot point: [9, 6] m: 0
我稍微改变了这个例子,p(8,1)到p(7,1)(我画了下面的点),然后发现p(7,2)将不会被生成到KdNode,因为第一个轴心点是(7,1),KdNode将把集合拆分为{[2,3],[4,7],[5,4],[7,1]}和{[9,6]},根据代码,这将使p(7,2)消失
我想知道在旋转点的同一条分割线上是否还有其他点(这里是垂直线交叉点(7,1)),应该包括哪一组p(7,2),以及何时必须将其作为KdNode
感谢您的阅读和帮助,我们将不胜感激
代码变更
return KdNode(d, split, self.nk2(s2, exset[:m]),self.nk2(s2, exset[m + 1:]))
到
return KdNode(exset[m], split, self.nk2(s2, exset[:m]),self.nk2(s2, exset[m + 1:]))
虽然split对我来说看起来很奇怪,但我正在努力包含缺失的一点。不过我还是希望听到更好的答案!谢谢大家!
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