找到由输入数字的数字形成的最大数字

Question

I am trying to write a function that return the biggest number formed by the digits from an input integer number. So if the input = 123584 output should be = 854321

My code is -

def maxNumber(inputNumber):
    x = len(str(inputNumber))
    max_number = []
    result= []
    while(x>0):
        max_number.append(inputNumber%10)
        inputNumber = inputNumber/10
        x -= 1
    while(x<(len(str(max_number)))):
        result.append(max(max_number))
        x += 1
    return result

print maxNumber(1238675)

and off-course the output is not as I want. Please help. I am eager to learn all possible way to do it.

Answer 1

The biggest number is formed by sorting the digits in descending order. This can be achived using the rverse=True parameter to sorted() :

def max_digit_permutation(n):
    return int("".join(sorted(str(n), reverse=True)))

Answer 2

def maxNumber(inputNumber):
    return int(''.join(sorted(str(inputNumber), reverse=True)))

Answer 3

This is more reliable than most answers given so far ;-)

def max_number(n):
    s = str(n)
    digits = sorted(s, reverse=n>0)
    return int(''.join(digits))

print max_number(231)    
print max_number(-231)    
print max_number(+231)    

And good point - I missed the option of doing it with number alone - here it is for completeness. :)

from math import *

def max_number(n):
    digit_count = int(log(abs(n+1),10)) + 1 
    digits = sorted([(n / 10 ** (x - 1) % 10)  for x in range(digit_count,0,-1) ], reverse=True)
    return reduce(lambda x, y:10*x + y, digits)

print max_number(1000)
print max_number(999)
print max_number(2345128)
print max_number(231) 

Answer 4

sort the string of number, reverse it, join it and convert to int

>>> x=123584
>>> int(''.join(sorted(str(x))[::-1]))
854321

Answer 5

You could just treat the number as a list of single digits and then sort the list in decreasing order.

What about something like this:

num = str(123584)
int(''.join(sorted(num, reverse=True)))