Replacing duplicate integers in an array

[steveballinger]

I'm trying to write a function that takes an array of unsorted positive integers N elements long.

The function should return the same array (no new allocations) with all duplicated integers replaced with -1 and moved to the end of the array.

So for example, the string:

1136788999

becomes ...

136789-1-1-1-1

Does anyone have a code snippet that accomplishes this? Sounds like a hash table could be the best approach here, but not sure.

Thanks much in advance!

~Steve

[iamthwee]

I'm trying to write a function that takes an array of unsorted positive integers N elements long.

The function should return the same array (no new allocations) with all duplicated integers replaced with -1 and moved to the end of the array.

So for example, the string:

1136788999

becomes ...

136789-1-1-1-1

Does anyone have a code snippet that accomplishes this? Sounds like a hash table could be the best approach here, but not sure.

Thanks much in advance!

~Steve

Yeah I'd agree with that. Go with the hasttable.

[steveballinger]

Yeah I'd agree with that. Go with the hasttable.

Thank you. I'm a bit new at this and having trouble getting started. So for the example given, how would you start? Very much obliged.

[lok_tan]

Before that, please confirm. What is the input parameter of the function? is it an array of integers? or a string?
since you mention that the function must return the same array (no allocation), meaning that the input parameter is also an array.
but in your example, you mention it about a string.

Regards,

Lok

[steveballinger]

Sorry. I misspoke. It is an array.

[lok_tan]

Sorry, forgot to asking.. is all the integers are 1-digit (0 to 9)?

regards,

Lok

[steveballinger]

Yes. All are 1-digits.

[lok_tan]

Easy then, no need to use any hashtable, just use array of boolean.

private bool[] flag = new bool[10];

each time you iterate the integer array, check against the flag array using the current integer value as it's index. if the flag[integer[loop_index]] == false, leave it as it is, then change it to true.
but if it's already true, meaning the integer value already exists, so shift the integer array contents by -1, started from the already exists integer value, and replace the last integer-array value with -1.

Hope that logic will help.

Regards,

Lok

[steveballinger]

That is easier and terrific advice. I'll give that a try. Thanks so much!

~Steve