我想通過解決項目歐拉問題來學習python。我卡在問題58.問題狀態因此:Python代碼凍結了我的電腦 - 項目歐拉58
Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed.
37 36 35 34 33 32 31
38 17 16 15 14 13 30
39 18 5 4 3 12 29
40 19 6 1 2 11 28
41 20 7 8 9 10 27
42 21 22 23 24 25 26
43 44 45 46 47 48 49
It is interesting to note that the odd squares lie along the bottom right diagonal, but what is more interesting is that 8 out of the 13 numbers lying along both diagonals are prime; that is, a ratio of 8/13 ≈ 62%.
If one complete new layer is wrapped around the spiral above, a square spiral with side length 9 will be formed. If this process is continued, what is the side length of the square spiral for which the ratio of primes along both diagonals first falls below 10%?
這是我寫的解決此問題的代碼。我利用primesieve來檢查素數,但我不知道設置primesieve的限制。所以我讓代碼告訴我什麼時候需要增加限制。代碼運行良好,限制爲10^8,但是當我將其設置爲10^9時,代碼凍結了我的PC,我必須重新啓動。不知道我做錯了什麼。如果您需要更多信息,請告訴我。謝謝!
def primesieve(limit):
primelist=[]
for i in xrange(limit):
primelist.append(i)
primelist[1]=0
for i in xrange(2,limit):
if primelist[i]>0:
ctr=2
while (primelist[i]*ctr<limit):
a=primelist[i]*ctr
primelist[a]=0
ctr+=1
primelist=filter(lambda x: x!=0, primelist)
return primelist
limit=10**7
plist=primesieve(limit)
pset=set(plist)
diagnumbers=5.0
primenumbers=3.0
sidelength=3
lastnumber=9
while (primenumbers/diagnumbers)>=0.1:
sidelength+=2
for i in range(3):
lastnumber+=(sidelength-1)
if lastnumber in pset:
primenumbers+=1
diagnumbers+=4
lastnumber+=(sidelength-1)
if lastnumber>plist[-1]:
print lastnumber,"Need to increase limit"
break
print "sidelength",sidelength," last number",lastnumber,(primenumbers/diagnumbers)
你可能會看看http://stackoverflow.com/q/2068372/344286關於改善你的篩子的一些提示 –
項目歐拉是強力的點不會解決問題,你需要做一些數學減少所需的計算量/存儲量。 –