How can I make a Function to compact an array with duplicate entries?
For example!
A function that will take a sorted array of integers and return the array compacted. That is, given an array containing: 1, 2, 6, 8, 8, 8, 9, 10, 10, when the function returns, the contents of the array should be: 1, 2, 6, 8, 9, 10.
This is NOT hw. I am trying to make a function that will do this.
How about:
array = array.Distinct().ToArray();
or, as a function:
private int[] RemoveDuplicates(int[] array)
{
return array.Distinct().ToArray();
}
then call it with:
array = RemoveDuplicates(array);
extension methods:
public static T[] RemoveDuplicates<T>(this T[] array)
{
return array.Distinct().ToArray();
}
public static List<T> RemoveDuplicates<T>(this List<T> list)
{
return list.Distinct().ToList();
}
using for array:
int[] array = new[] {1, 3, 4, 3};
array = array.RemoveDuplicates();
using for list:
List<int> list = new List<int> {1, 3, 4, 3};
list = list.RemoveDuplicates();
The most straightforward way is probably with Linq
array = array.Distinct().ToArray()
However, Linq is not always the fastest approach.
If you do not wish to use Linq, you can do something like this (untested, but close)
List<int> compacted = new List<int>();
// If array is not a local variable:
// Assign to a variable to avoid re-evaluating the property every loop iteration
// Otherwise use array.Length as the loop termination condition to enable array
// bounds check elimination. Thanks @Harold for the insight
// http://blogs.msdn.com/b/clrcodegeneration/archive/2009/08/13/array-bounds-check-elimination-in-the-clr.aspx
int max = array.Length;
int last = 0;
for (int i=0; i < max; i++)
{
if (i == 0)
{
compacted.Add(array[i]);
last = array[i];
}
else
{
if (array[i] != last) compacted.Add(array[i]);
last = array[i];
}
}
array = compacted.ToArray();
array.Length here would actually enable array bounds check elimination.
for(int i = 0; i < Array.Length; i++) etc; is a special case in which the JIT compiler doesn't bounds-check array accesses indexed by i.
int?for thepreviousand initialize it to null, and then you can be sure that the initial value will never be equal thecurrentvalue.