Question

This is with regard to previous question posted a while ago
Remove -1 entry from integer array

I know there are blazing fast solutions , one line answers as posted in answer section to previous posted question , but being a newbie I tried doing by for loops.

  int[] arr = new int[]{ 1, -1, -1, 1 };
            int[] new_arr;
            int index = 0;
            for (int i = 0; i < arr.Length; i++)
            {
               // Console.WriteLine(arr[i]);
                if (arr[i] == -1)
                    continue;
                else
                    new_arr[index++] = arr[i];
            }

I am getting error

Use of unassigned local variable ‘new_arr’

what am I doing wrong.

EDIT

        int[] arr = new int[]{ 1, -1, -1, 1 };
        int[] new_arr = new[arr.Length]; //Error being shown at this line
        int index = 0;
        for (int i = 0; i < arr.Length; i++)
        {

            if (arr[i] == -1)
                continue;
            else
                new_arr[index++] = arr[i];
        }

        for(int j=0;j<new_arr.Length;j++)
            Console.WriteLine(new_arr[j]);

Answer 1

You haven’t initialized your array new_arry. You need to specify its size.

int[] new_arr = new int[10];

Inside your code you are doing:

new_arr[index++] = arr[i];

Here since the array has not been initialized and you are trying to use it, that is why you are getting this error.

You may use List<int> instead of the array, because it seems you are not sure about the Size of the array in your code.

So your code would be:

int[] arr = new int[]{ 1, -1, -1, 1 };
List<int> tempList = new List<int>();
int[] new_arr;
int index = 0;
for (int i = 0; i < arr.Length; i++)
      {
       // Console.WriteLine(arr[i]);
         if (arr[i] == -1)
              continue;
         else
            tempList.Add(arr[i]);
      }
new_arr = tmepList.ToArray();

Or the complete code can be shorten to:

int new_arr = arr.Where(r=> r!= -1).ToArray();