python实现求第K小

#encoding:utf-8
_author_ = "Wang Wenchao"
import heapq
#该包封装了最小堆，想要用最大堆则用相反数
'''
升序数组第一个是1，后续为若干连续的素数，
对于里面的元素m和n满足m<n，都对应了一个有理数m/n，
现在给定一个数组和一个K，要求返回第K小的有理数
1
3 1 2 3 5   第一个为K
输出为  0.4 2 5
'''
n=int(raw_input())
for i in range(n):
    line=raw_input().split(' ')
    K=int(line[0])
    res = [-1] *K
    heapq.heapify(res)
    left=right=0
    line.pop(0)
    arr=[int(x) for x in line]
    #print arr
    for j in range(len(arr)-1):
        for h in range(j,len(arr)):
            dif=-float(arr[j])/arr[h]
            #print res
            if dif>min(res):
                left=arr[j]
                right=arr[h]
                heapq.heapreplace(res,dif)
    print -min(res),left,right

 

下面是自动计算某个范围的第K小商

#encoding:utf-8
_author_ = "Wang Wenchao"
import sys
import heapq

def FindMinK(K,arr):
    print arr
    res = [-1] *K
    heapq.heapify(res)
    left=right=0
    #print arr
    for j in range(len(arr)-1):
        for h in range(j,len(arr)):
            dif=-float(arr[j])/arr[h]
            #print res
            print -dif
            if dif>min(res):
                print -dif,"*****"
                left=arr[j]
                right=arr[h]
                heapq.heapreplace(res,dif)
    return -min(res),left,right


def IsPrim(N):
    k=int(pow(N,1.0/2))
    for i in range(2,k+1):
        if N%i==0 and i!=N:
            return 0
    return 1
def main(argv):
    with open('primes','w') as f:
        count=0
        begin=int(argv[1])
        end=int(argv[2])
        K=int(argv[3])
        for i in range(begin,end+1):
            if IsPrim(i)==1:
                print i
                f.write(str(i)+'\n')
                count+=1
        print '共',count,'个质数'
        f.write('共'+str(count)+'个质数\n')
    arr=[1]
    with open('primes', 'r') as f:
        lines=f.readlines()
        print lines
        for c in range(len(lines)-1):
            arr.append(int(lines[c].strip()))
    minK,left,right=FindMinK(K,arr)
    print 'minK=',minK,'left=',left,'right=',right
if __name__ == '__main__':
    #main(sys.argv)
    main([0,2,6,3])