Python array sort

Question

From a CTF challenge, a easy pwn(elf). I could probably have done it in better way, but anyway I ended up with the flag in a array looking like this.

['4:a', '27:a', '33:a', '39:b', '5:c', '31:c', '44:c', '45:c', '18:d', '37:d', '2:e', '21:e', '25:e', '29:e', '36:e', '46:e', '35:g', '3:h','32:h', '17:i', '6:k', '10:l', '24:l', '9:n', '34:n', '22:o', '16:p', '20:p', '23:p', '28:r', '13:s', '42:s', '47:s', '48:s', '14:t', '15:u','43:u', '1:w', '11:y', '40:y', '8:O', '7:{', '49:}', '12:_', '19:_', '26:_', '30:_', '38:_', '41:_','0:$']

Is it possible to sort this array in easy way?

It's easy to sort using Python sort function. What criteria do you want to use in sorting? If you just want each item treated as a string and sorted in alphabetical order than sorted(your-array) will do that. Also: your.array.sort() to sort in-place. — DarrylG
– DarrylG, Commented Dec 26, 2019 at 11:52
The first char in the flag is 0:$ the second is 1:w, so I want to sort it by the numbers — r4113
– r4113, Commented Dec 26, 2019 at 11:57
@r4113 You may accept the answer, if it solves your problem. If not, feel free to ask any question. — Rohit Lal
– Rohit Lal, Commented Jun 20, 2020 at 11:49

Atul · Accepted Answer · 2019-12-26 12:14:24Z

flagArray = ['4:a', '27:a', '33:a', '39:b', '5:c', '31:c', '44:c', '45:c', '18:d', '37:d', '2:e', '21:e', '25:e', '29:e', '36:e', '46:e', '35:g', '3:h','32:h', '17:i', '6:k', '10:l', '24:l', '9:n', '34:n', '22:o', '16:p', '20:p', '23:p', '28:r', '13:s', '42:s', '47:s', '48:s', '14:t', '15:u','43:u', '1:w', '11:y', '40:y', '8:O', '7:{', '49:}', '12:_', '19:_', '26:_', '30:_', '38:_', '41:_','0:$']```

def getNumber(x):
  return int(x.split(":")[0])

sorted(flagArray, key = getNumber)

>>>
['0:$',
 '1:w',
 '2:e',
 '3:h',
 '4:a',
 '5:c',
 '6:k',
 '7:{',
 '8:O',
 '9:n',
 '10:l',
 '11:y',
 '12:_',
 '13:s',
 '14:t',
 '15:u',
 '16:p',
 '17:i',
 '18:d',
 '19:_',
 '20:p',
 '21:e',
 '22:o',
 '23:p',
 '24:l',
 '25:e',
 '26:_',
 '27:a',
 '28:r',
 '29:e',
 '30:_',
 '31:c',
 '32:h',
 '33:a',
 '34:n',
 '35:g',
 '36:e',
 '37:d',
 '38:_',
 '39:b',
 '40:y',
 '41:_',
 '42:s',
 '43:u',
 '44:c',
 '45:c',
 '46:e',
 '47:s',
 '48:s',
 '49:}']

The array will be sorted by the number part of each element

A oneliner approach would be to use a lambda function

sorted(flagArray, key = lambda x : int(x.split(":")[0]))

Rohit Lal · Accepted Answer · 2019-12-27 10:13:37Z

2

One liner solution

You can use inbuilt python functions sort or sorted along with lambda function.

my_list = ['4:a', '27:a', '33:a', '39:b', '5:c', '31:c', '44:c', '45:c', '18:d', '37:d', '2:e', '21:e', '25:e', '29:e', '36:e', '46:e', '35:g', '3:h','32:h', '17:i', '6:k', '10:l', '24:l', '9:n', '34:n', '22:o', '16:p', '20:p', '23:p', '28:r', '13:s', '42:s', '47:s', '48:s', '14:t', '15:u','43:u', '1:w', '11:y', '40:y', '8:O', '7:{', '49:}', '12:_', '19:_', '26:_', '30:_', '38:_', '41:_','0:$']

Inplace Sort

my_list.sort(key=lambda k: k.split(':')[0])

Getting sorted list as a copy

sorted_list = sorted(a, key=lambda k: k.split(':')[0])

edited Dec 27, 2019 at 10:13

answered Dec 26, 2019 at 14:03

Rohit Lal

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