Python：每日一题 205,Python交流,技术交流,鱼C论坛

冬雪雪冬 发表于 2018-9-2 10:54:27

Python：每日一题 205

本帖最后由冬雪雪冬于 2018-9-8 19:05 编辑

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题目：
本题又是求素数（质数）的题目，这回采用筛法来计算。关于筛法的原理，这里引用了百度百科的一段话：
用筛法求素数的基本思想是：把从1开始的、某一范围内的正整数从小到大顺序排列， 1不是素数，首先把它筛掉。剩下的数中选择最小的数是素数，然后去掉它的倍数。依次类推，直到筛子为空时结束。
看看大家谁的程序更简单，更快捷。
为了简便就求出200以内的素数。

凌九霄 发表于 2018-9-2 11:04:24

本帖最后由凌九霄于 2018-9-4 01:29 编辑

本代码中，最耗时的是sorted排序，占整个运行时间的54%左右。
import timeit

P= '''
nums = [ x for x in range(2, 10000) ]
for i in range(len(nums)):
if i < len(nums):
   nums = sorted(list(set(nums) - set([ nums[ i ] * x for x in range(2, nums[-1]//nums + 1) ])))
else:
   print(nums)
   break
'''
print('运行时间：',timeit.timeit(stmt=P,number=1))

塔利班 发表于 2018-9-2 11:08:42

def fun205(n):
r=[]
f=list(range(2,n+1))
while f:
r.append(f.pop(0))
f=]
return r

拉了盏灯 发表于 2018-9-2 11:21:56

本帖最后由拉了盏灯于 2018-9-2 12:16 编辑

我这个还是有点慢，参考大神的程序，
def p(n):
l =
for i in range(3,n,2):
   if i in l:
         for i in (i for i in range(2*i,n,i) if i in l):
            l.remove(i)
return l

Legend丶Hu 发表于 2018-9-2 11:55:18

a = []
for i in range(100):
a.append(i)

for i in range(2,51):
if a:
   j = i + i
   while j < 100:
         a = 0
         j+=i
for i in range(2,100):
if a:
   print(a,end = " ")

靳泽宇 发表于 2018-9-2 12:20:07

本帖最后由靳泽宇于 2018-9-2 12:22 编辑

for x in range(1, 200):
for i in range(2, x):# ------------------从2开始一直除到它自身的前一个数
   if x % i == 0:# ---------------------如果有余数为零，跳出循环
         break
else:# ----------------------------------全部除完没有余数为零的话，输出这个数字
   if x != 1:
         print(x)

黑白、 发表于 2018-9-2 15:33:53

def odd_number():
num = 1
while True:
   num = num + 2
   yield num
def screen(num):
return lambda x: x % num > 0
def fun205():
   yield 2
   temp = odd_number()
   while True:
         num = next(temp)
         yield num
         temp = filter(screen(num),temp)

numMAX = int(input('输入最大范围:'))
for each in fun205():
if each < numMAX:
   print(each)
else:
   break

子沙发表于 2018-9-2 16:43:33

def fun_205(x):
list1=list(range(2,x+1))
for i in list1:
   flag=0
   for j in range(2,i//2+1):
         if i%j==0:
            flag=1
   if flag==0:
         for k in range(2,x//i+1):
            if k*i in list1:
               list1.remove(k*i)
print(' ',*list1)
fun_205(200)

在东边 发表于 2018-9-2 17:43:23

def primes(num):
it = iter(range(2, num + 1))
n = next(it)
while n <= num:
   yield n
   it = filter(lambda x, n=n: x % n, it)
   n = next(it)

print(', '.join(map(str, primes(200))))

zhou995287902 发表于 2018-9-2 17:52:39

import time
def isPrime(num):
if num<2:
   return False
else:
   for i in range(2,num//2+1):
         if num % i==0:
            return False
   else:
         return True
def fun205(num):
index=0
while index<len(num):
   if isPrime(num):
         for i in num:
            if i%num==0:
               num.remove(i)
   else:
         num.remove(num)
   index+=1
print(num)

t1=time.time()
nums=[]
for i in range(2,201):
nums.append(i)

fun205(nums)
print('耗时：',time.time()-t1)

久疤K 发表于 2018-9-2 20:09:10

>>> def fun( n = 200 ):
ns = list(range(n+1))
ns =
for i in range(n):
if not ns:
continue
ns = * len(ns)
return

>>> fun()

>>>

JessiFly 发表于 2018-9-2 20:18:35

本帖最后由 JessiFly 于 2018-9-2 20:19 编辑

def fun205(n):
primefilter =
primes = []
while primefilter:
   min_p = primefilter.pop(0)
   primes.append(min_p)
   i = min_p
   while i <= (n//min_p):
         mul_p = min_p * i
         if mul_p in primefilter:
            primefilter.remove(mul_p)
         i += 1
for each in primes:
   print(each,end=' ')

if __name__ == '__main__':
fun205(200)

archlzy 发表于 2018-9-2 21:41:04

import math

def q205(num):
temp = list(range(2, num+1))
temp_bool = * len(temp)
for i in range(2, int(math.sqrt(num)) + 1):
   for j in range(2, num // i+1):
         if temp_bool != False:
            temp_bool = False
return for i in range(len(temp_bool)) if temp_bool]

天圆突破 发表于 2018-9-2 23:12:41

本帖最后由天圆突破于 2018-9-2 23:19 编辑

def func205(n):
collection, result = list(range(2, n+1)), []
while collection:
result.append(collection)
collection = list(filter(lambda x:x%result[-1], collection))
return result

if __name__ == '__main__':
print(func205(400))

晓屁屁 发表于 2018-9-3 14:16:26

x =
for i in x[:]:
for y in range(2,200):
   z = i * y
   try:
         x.remove(z)
   except ValueError:
         pass
print(x)

chongchuigu 发表于 2018-9-3 15:53:29

本帖最后由 chongchuigu 于 2018-9-3 15:55 编辑

def a205(n):
list1=[]
for i in range(2,n+1):
   list1.append(i)
list2=list1[:]
for i in list1:
   j=2
   if i not in list2:
         continue
   else:
         s=i*j
         while s<=n:
            if s in list2:
               list2.remove(s)
            j+=1
            s=i*j
return list2
print(a205(2000))

绝境凤凰 发表于 2018-9-3 16:10:26

啊啊啊啊啊啊啊啊啊啊a

祥哥威武 发表于 2018-9-3 17:20:57

def getNumber(x):
list0 = list((i for i in range(2, x+1)))
for i in list0[:]:
   for j in list0[:]:
         if j <= i:
            continue
         if j % i == 0:
            list0.remove(j)
return list0
print(getNumber(30))

claws0n 发表于 2018-9-3 18:10:21

尝试了 5 个版本，没问题{:5_91:}
200 测不出时间
import time

n = 2000

## code 1
start_time = time.time()

prime = []
check = []
k = int(n**0.5)
for i in range(3,n+1,2):
if i not in check:
   prime.append(i)
   check.append(i)
   if i <= k:
         while check[-1] < n:
            check.append(check[-1]+i+i)
if n > 1:
prime.insert(0,2)
elapsed_time1 = ( time.time() - start_time )*1000

## code 2
start_time = time.time()

prime2 =
if n > 1:
prime2.insert(0,2)
k = int(n**0.5)
for i in range(3,k+1,2):
j = i
while j < n - i:
   j += i+i
   try:
         prime2.remove(j)
   except:
         pass

elapsed_time2 = ( time.time() - start_time )*1000

## code 3
start_time = time.time()
prime3 = []
check2 = []
k = int(n**0.5)
for i in range(3,n+1,2):
if i not in check2:
   prime3.append(i)
   if i <= k:
         for j in range(i, n, i+i):
            if j not in check2:
               check2.append(j)
if n > 1:
prime3.insert(0,2)
elapsed_time3 = ( time.time() - start_time )*1000

## code 4
start_time = time.time()

prime4 =
if n > 6:
prime4.insert(0,7)
if n > 4:
prime4.insert(0,5)
if n > 2:
prime4.insert(0,3)
if n > 1:
prime4.insert(0,2)

for i in range(11,int(n**0.5)+1,2):
j = i
while j < n - i:
   j += i+i
   if j in prime4:
         prime4.remove(j)

elapsed_time4 = ( time.time() - start_time )*1000

## code 5
start_time = time.time()

prime5 =
if n > 6:
prime5.insert(0,7)
if n > 4:
prime5.insert(0,5)
if n > 2:
prime5.insert(0,3)
if n > 1:
prime5.insert(0,2)

for i in range(11,int(n**0.5)+1,2):
j = i*i
while j < n:
   if j in prime5:
         prime5.remove(j)
   j += i+i

elapsed_time5 = ( time.time() - start_time )*1000

print('len1',len(prime),len(check))
print('elapsed time = {} ms'.format(elapsed_time1))

print('len2',len(prime2))
print('elapsed time = {} ms'.format(elapsed_time2))

print('len3',len(prime3),len(check2))
print('elapsed time = {} ms'.format(elapsed_time3))

print('len4',len(prime4))
print('elapsed time = {} ms'.format(elapsed_time4))

print('len5',len(prime5))
print('elapsed time = {} ms'.format(elapsed_time5))
n = 2000
len1 303 1441
elapsed time = 22.9947566986084 ms
len2 303
elapsed time = 17.994403839111328 ms
len3 303 710
elapsed time = 40.98987579345703 ms
len4 303
elapsed time = 7.997751235961914 ms
len5 303
elapsed time = 4.9991607666015625 ms
n = 200
len1 46 129
elapsed time = 1.0006427764892578 ms
len2 46
elapsed time = 0.0 ms
len3 46 59
elapsed time = 0.0 ms
len4 46
elapsed time = 0.0 ms
len5 46
elapsed time = 0.0 ms
>>> prime5

应该没犯规吧？{:5_92:}{:5_92:}
筛选生成、筛选结果

Chysial 发表于 2018-9-3 19:20:52

代码：
# 生成1`200的数，直接生成，采用列表的形式
number = []
prime = []
for i in range(1,201):
number.append(i)

# 排序
number.sort()

# 筛选

for each in range(199):
if number == 1:
   number.pop(each)

while number:
prime.append(number)
for each in number:
   if each % number ==0:
         number.remove(each)
# 输出结果
print(prime)

结果：

页: [1] 2 3

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Python：每日一题 205