求素数和杨辉三角

求素数

for循环

##  把所有偶数去掉
import datetime

start = datetime.datetime.now()

n=100000
count=1
for i  in range (3,n,2):    ##
    for j in range(3,int(i ** 0.5)+1,2):  ## 整除的数
        if  i%j==0:
            break
        
    else:
        count += 1
delta = (datetime.datetime.now() - start).total_seconds()
print(count)
print(delta)

列表解法

import datetime

start = datetime.datetime.now()
n=100000
primenumber=[2]
for i in range (3,n,2):
    flag = False
    k = i**0.5
    for j in primenumber:
        if j > k:    
            flag = True
            break
        if i % j == 0:  #  不是质数
            flage = False
            break
    if flag :
        primenumber.append(i)
delta = (datetime.datetime.now() - start).total_seconds()
print(count)
print(delta)

孪生素数解法

import datetime

start = datetime.datetime.now()


l1=[]
l2 = [2,3,5]
num = 5
add = 2
count = 3
n=100000

while num < n: ##3  +2 5  +2 7  +4 11 +2  13  +4  17   19
    if num%5 !=0:
        l1.append(num)
    num = num+ add  
    add = 4  if add == 2  else 2
for i in  l1:
    flag = False
    k= int(i**0.5)
    for j in  l2:
        if j > k:
            flag=True
            break
        if i%j == 0:
            flag= False
            break
    if flag :
        l2.append(i)
        count += 1
delta = (datetime.datetime.now() - start).total_seconds()
print(count)
print(delta)

杨辉三角

杨辉三角 单行覆盖

## 1 先创建一个大列表    [1]*n   
l3 = [1]*(6)
for i in range (6):
    old = 1
    for j in range (i//2):
        val = old+l3[j+1]
        old = l3[j+1]
        l3[j+1]= val
        l3 [i-j-1]=val
    print(l3)

大列表套小列表

 
 triangle=[[1],[1,1]]

for i in range (1,6):
 pre = triangle[i]
 cur=[1]*(i+2)
 
 for j in range (i//2+1):
     val=(pre[j]+pre[j+1])
     cur[j+1] =val
     cur[-j-2] = val
 
 triangle.append(cur)
print(triangle)