Question

How to make the last element of an array null?(c++)So for my data structures class, we are working in c++. We are supposed to create a function that takes in an array, shifts everything to the left and leaves the original final element as null. Now I haven't found any simple way to convert them to null so I was just converting them to "0".I was seeking help on how to modify my code such to make the final element a null value.

We are also testing our code with catch 2,so I will include my test case that isn't running. Any help would be greatly appreciated. I was also seeking help on how to get the function to be called and properly function

Thank you! :)

edit:Sorry if the question was ambiguous

here is the code I have so far.

```
int * left_shift(int arr[],int n)
{
for(int i = 0 ; i {
       if(i==n-1){ arr[i] = 0; } // make last element null
       arr[i] = arr[i+1]; //shift element to the right
   }
   return arr; //function then returns modifed array
}

```

and here are the failing tests,that are saying I am converting the file incorrectly. I don't quite understand the error message to be honest

```
TEST_CASE("left_shift","[Lab1]"){

       SECTION("ex1")//test one
       {
           int arr[] = {1,2,3,4};//initial array
           int n = sizeof(arr)/sizeof(int);
          
           int r[]= {left_shift(&arr,n)};
           CHECK(r[n-1] == 0);
   }

}
```

Thanks again !

Answer 1

Hi,

Please find the solution below:
------------------------------

There is a small bug in the code. After checking for the final last element and assigning it to zero,
We need to break the code.

Note: On assumption that the last element is set to zero.

if(i==n-1){
           arr[i] = 0;
           break;
       } // make last element null

Otherwise, the code shifts some junk content to the last element in the next line.

arr[i] = arr[i+1]; //shift element to the right

The above would execute and overrides the assignment of zero in the last element.

-----

The function returns the base address of the array. Use of pointers would be helpful in the test case.

Sample code:

// Example program
#include <iostream>

int* left_shift(int arr[],int n)
{
for(int i = 0 ; i<n;i++) {
       if(i==n-1){
           arr[i] = 0;
           break;
       } // make last element null
       arr[i] = arr[i+1]; //shift element to the right
   }
   return arr; //function then returns modifed array
}

int main()
{
int arr[] = {1,2,3,4};//initial array
int n = sizeof(arr)/sizeof(int);
        
int* p;
p=left_shift(arr,n);

for ( int i = 0; i < n; i++ ) {
      std::cout << *(p + i) << "\n" ;
   }

}

------------------------------

Hope this helps.