[交流] Euler 工程 第三十六题： 已有3人参与

Originally posted by libralibra at 2011-07-08 01:17:59:
发现reverse的bin string要等于原来的,最后一位必是1,所以原来十进制肯定是奇数,加上这个条件可以节省近一半时间

[code]#! /usr/bin/env python

from mytictoc import tic, toc

def euler36():
    tic ...

# Project Euler Problem 36
#

def checkBinaryReverse(n):
    s = bin(n)[2:]
    r = s[::-1]
    if r == s:
        return True
    return False

# 2-, 3-, 4-digits
for x in xrange(1, 10, 2):
    # 2-digits
    n = int("%d"*2 % (x, x))
    if checkBinaryReverse(n):
        print n, "=>", bin(n)[2:]

    # 3-, 4-digits
    for y in xrange(1, 10):
        # 3-digits
        n = int("%d"*3 % (x, y, x))
        if checkBinaryReverse(n):
            print n, "=>", bin(n)[2:]
        # 4-digits
        n = int("%d"*4 % (x, y, y, x))
        if checkBinaryReverse(n):
            print n, "=>", bin(n)[2:]

        # 5-, 6-digits
        for z in xrange(1, 10):
            # 5-digits
            n = int("%d"*5 % (x, y, z, y, x))
            if checkBinaryReverse(n):
                print n, "=>", bin(n)[2:]
            # 6-digits
            n = int("%d"*6 % (x, y, z, z, y, x))
            if checkBinaryReverse(n):
                print n, "=>", bin(n)[2:]

15351 => 11101111110111
33 => 100001
313 => 100111001
32223 => 111110111011111
39993 => 1001110000111001
53235 => 1100111111110011
53835 => 1101001001001011
585 => 1001001001
585585 => 10001110111101110001
717 => 1011001101
73737 => 10010000000001001
7447 => 1110100010111
99 => 1100011

IDLE 2.6.6      
>>> print sum([_x for _x in xrange(1,1000001) if str(_x)==str(_x)[::-1] and str(bin(_x))[2:]==str(bin(_x))[2:][::-1]])
872187
>>>

# Project Euler Problem 36
#

def checkBinaryReverse(n):
    s = bin(n)[2:]
    r = s[::-1]
    if r == s:
        return True
    return False

# odd digits
for x in xrange(1, 1000):
    n = int(str(x)+str(x)[::-1])
    if checkBinaryReverse(n):
        print n, "=>", bin(n)[2:]

# even digits
for x in xrange(1, 100):
    for y in xrange(10):
        n = int(str(x)+str(y)+str(x)[::-1])
        if checkBinaryReverse(n):
            print n, "=>", bin(n)[2:]