#求10萬內的所有素數(9592)
print(2)
count = 1
for i in range(3,100000):
for j in range(2,i):
if i%j ==0:
break
if j==i-1:
print(i)
優化:
count = 1
for i in range(3,100000,2):#跳過所有偶數
for j in range(2,i):
if i%j ==0:
break
if j==i-1:
count +=1
print(count)
再優化:
count = 1
for i in range(3,100000,2):
for j in range(2,int(i**0.5)+1):#便利到i的開平方
if i%j ==0:
break
else:
count +=1
print(count)
再再優化:
#由於數學成績有限,方法來自網上
count = 2 #大於等於5的素數一定和6的倍數相鄰,所以2、3不在循環內統計,
n = 100000
for num in range(4,n):
if num%6 != 1 and num%6 !=5:
continue
else:
snum = int(num**0.5+1)
for i in range(5,snum):
if not num%i:
break
else:
count +=1
print(count)
再再再優化:
#求10萬內的所有素數
count = 2 #大於等於5的素數一定和6的倍數相鄰,所以2、3不在循環內統計,
n = 100000
for num in range(4,n):
if num%6 != 1 and num%6 !=5:
continue
else:
snum = int(num**0.5+1)
for i in range(5,snum,2):
if not num%i:
break
else:
count +=1
print(count)