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holmescn

½ð³æ (ÕýʽдÊÖ)

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ÓàÔó³É(½ð±Ò+3, ³ÌÐòÇ¿Ìû+1): ¹ÄÀø½»Á÷£¡ 2011-07-11 20:42:48
PythonÇî¾Ù
CODE:
# Project Euler Problem 37
#

# Gen a prime list
from math import sqrt
UBound = 100000
primes = range(2, UBound)
for x in primes:
    if x > 0:
        for n in xrange(2*x, UBound, x):
            primes[n-2] = 0

# change to a set to make "not in" faster
primes = set([x for x in primes if x > 0])

# Check each prime
for x in primes:
    if x > 10:
        s = str(x)
        flag = True
        for i in xrange(1, len(s)):
            # if any truncated number is not
            # a prime, break and set fail
            if int(s[i:]) not in primes or int(s[:len(s)-i]) not in primes:
                flag = False
                break
        if flag:
            print x

23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397

ºÍÊÇ748317

[ Last edited by holmescn on 2011-7-9 at 09:52 ]
2Â¥2011-07-08 23:22:21
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libralibra

ÖÁ×ðľ³æ (ÖøÃûдÊÖ)

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¡ï ¡ï ¡ï ¡ï
Сľ³æ(½ð±Ò+0.5):¸ø¸öºì°ü£¬Ð»Ð»»ØÌû
xzhdty(½ð±Ò+1): »¶Ó­³£À´³ÌÐòÓïÑÔ¿´¿´ 2011-07-09 07:01:26
ÓàÔó³É(½ð±Ò+2, ³ÌÐòÇ¿Ìû+1): »¶Ó­³£À´³ÌÐòÓïÑ԰棡 2011-07-11 20:43:27
11¸ö°¡ÐÖµÜ,ÄãÀ´¸ö7¸ö,ÎÒÒÔΪÎÒ¸ã´íÁË
Find the sum of the only eleven primes that are both truncatable from left to right and right to left.

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Éú³ÉËØÊýÁбíÎÒûÓÐɾ³ý·ÇËØÊý,Ö±½ÓÖÃ0,ÏÂÃæÓÃ[]>0ÅжϵÄ
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IDLEÐèÒª2.9s×óÓÒ
CODE:
11 748317
[23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397]
Elapsed time: 1.97395228 seconds

CODE:
#! /usr/bin/env python

from mytictoc import tic, toc

tic()

# produce prime list
stop = 1000000
pmlist = range(stop+1)
pmlist[:2] = [0,0]
i = 2
while i*i<=stop:
    if pmlist[i]>0:
        for j in xrange(2*i,stop+1,i):
            pmlist[j] = 0
    i += 1

nums = []
for i in xrange(23,stop+1):
    if pmlist[i]>0 and '0' not in str(i): # isprime and don't contain 0
        # get all sub number
        allnum = []
        for j in xrange(1,len(str(i))):
            allnum.extend([int(str(i)[:j]),int(str(i)[-j:])])
        # check all sub number
        if all([pmlist[x]>0 for x in allnum]):
            nums.append(i)

# print result
print len(nums),sum(nums)
print nums
        
toc()

[ Last edited by libralibra on 2011-7-9 at 01:05 ]
matlab/VB/python/c++/Javaд³ÌÐòÇë·¢QQÓʼþ:790404545@qq.com
3Â¥2011-07-09 00:18:33
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