2014-10-27 20:10:17 -04:00

35 lines
917 B
Python
Executable File

def quickSelect(seq, k):
# this part is the same as quick sort
len_seq = len(seq)
if len_seq < 2: return seq
ipivot = len_seq // 2
pivot = seq[ipivot]
smallerList = [x for i,x in enumerate(seq) if x <= pivot and i != ipivot]
largerList = [x for i,x in enumerate(seq) if x > pivot and i != ipivot]
# here starts the different part
m = len(smallerList)
if k == m:
return pivot
elif k < m:
return quickSelect(smallerList, k)
else:
return quickSelect(largerList, k-m)
if __name__ == '__main__':
# Checking the Answer
seq = [10, 60, 100, 50, 60, 75, 31, 50, 30, 20, 120, 170, 200]
# we want the middle element
k = len(seq) // 2
# Note that this only work for odd arrays, since median in
# even arrays is the mean of the two middle elements
print(quickSelect(seq, k))
import numpy
print numpy.median(seq)