----------------------------------- rar Sat Jan 30, 2010 10:07 am A Particular Sort ----------------------------------- So my most recent assignment in school is apparently based on some sort of Children's Game. I never played this game, but... The assignment requires that I take in any user-defined amount of numbers and use them to make the highest possible integer. So as an example: Input: (numbers = 3) 803 97 3 Output: 978033 (sorting it 97, 803, 3) So the numbers have to stay together...but as you can see, the numbers aren't sorted largest -> smallest, but they are sorted by the way the digits will make the output numbers the largest. So I've taken input from the user to define the size of an array scanf("%d", &n); int Array[n]; And I've sorted the array elements from greatest to least using a simple bubble sort (being the sort we've learned). However, that was just a start. My next step was to check if the first digit is highest, then the second digit...and to of course use a bubble sort to continue to sort it accordingly. However, the way I was doing it, I had if statements programmed for each interval of possibility. I'd check 10 but 100 but r by digit rather than by value. The idea here is to change your comparison function, not your sort. ----------------------------------- Alexmula Sat Jan 30, 2010 12:18 pm RE:A Particular Sort ----------------------------------- yup. comparing strings is the way to go. take a look at the string.h library. once you are done submit your code to the uva online judge to make sure it works for all cases :D ----------------------------------- rar Sun Jan 31, 2010 12:10 am Re: RE:A Particular Sort ----------------------------------- Well, you can convert all these numbers to strings and then use a string comparison because strings are compared l->r by digit rather than by value. The idea here is to change your comparison function, not your sort. That's genius!! We haven't learned a lot about the string.h library yet, but there's no specifications on how to solve the problem so I'm sure that would be perfect! Thanks!! Yeah I knew the sorting method would be the same, but I figured if I kept coding for endless possibilities, it wasnt''t efficient coding. ----------------------------------- Euphoracle Sun Jan 31, 2010 12:21 am RE:A Particular Sort ----------------------------------- Well the alternative is tricky floating point math involving log base 10 and dividing/flooring by powers of 10 to extract digits... but that's not as straight forward as this is. ----------------------------------- rar Sun Jan 31, 2010 12:36 pm RE:A Particular Sort ----------------------------------- So I don't know a lot about string comparison yet.... I searched and found this: [code]int memcmp(const void *s1, const void *s2, size_t n);[/code] Would this be what I want to use for comparing? I read up on it and I think it returns 0. I don't know how I would use that... Essentially what I want to do is compare strings to see which one is greater...though is that really what I want to do? ----------------------------------- DtY Sun Jan 31, 2010 12:50 pm RE:A Particular Sort ----------------------------------- String comparison is really easy. `memcmp` will work, but you need to give it the length of the buffer, `strcmp` will do the same thing, but wont need the length. I don't know how much you've learned about strings, but here's how they work. Strings are arrays of `char`s, all you get is the syntax for assigning a string char myString This will allocate 14 bytes of memory, and fill it with "Hello, World!" followed by a null (character with the value 0). Because there is no way of getting the length of an array in C, anything working with arrays need to do one of the following: a) Store the length of the array in the array b) Have a special value to mark the end of the array c) Have a fixed length that every array will use (This list will come up again when you do socket programming) C uses option `a` for string functions. Pascal, and some similar languages (for example, Turing) used `b`, but was left with the maximum length of strings being 255 characters. So, when you use double quotes to fill a string, it automatically adds a null at the end of the string. Which works, for strings. This will not work for binary data though, because it could have a null in it. So, you end up with two funtions, `memcmp` which compares blocks of memory and takes the length of them, and `strcmp` which takes two blocks of memory and finds the length before comparing. http://www.cplusplus.com/reference/clibrary/cstring/strcmp/ ----------------------------------- rar Sun Jan 31, 2010 3:02 pm RE:A Particular Sort ----------------------------------- So I believe that I should use strcmp then, based on what you've explained. What exactly does the function compare though? And are you saying that if it can't compare "992" and "45" because they aren't the same length? Or am I misunderstanding... ----------------------------------- DtY Sun Jan 31, 2010 5:08 pm RE:A Particular Sort ----------------------------------- It will compare them the same way that memcmp would compare them, but it will figure out the length. I am pretty sure that it will only compare up to the shorter of the two strings (and if they're the same up to that point, the shorter one would be less than the longer one). ----------------------------------- rar Sun Jan 31, 2010 6:58 pm RE:A Particular Sort ----------------------------------- I guess what I mean to ask is...what will they return? ----------------------------------- DtY Sun Jan 31, 2010 7:53 pm RE:A Particular Sort ----------------------------------- Ah, the same thing as memcmp if you do strcmp(A, B); it will return =0 if A == B >0 if A > B 0 and