Return an Array in C

What is an Array?

An array is a type of data structure that stores a fixed-size of a homogeneous collection of data. In short, we can say that array is a collection of variables of the same type.
For example, if we want to declare 'n' number of variables, n1, n2...n., if we create all these variables individually, then it becomes a very tedious task. In such a case, we create an array of variables having the same type. Each element of an array can be accessed using an index of the element.
Let's first see how to pass a single-dimensional array to a function.
Passing array to a function. 
    
        #include   
            void getarray(int arr[])  
            {  
                printf("Elements of array are : ");  
                for(int i=0;i<5;i++)  
                {  
                    printf("%d ", arr[i]);  
                }  
            }  
            int main()  
            {  
               int arr[5]={45,67,34,78,90};  
               getarray(arr);  
               return 0;  
            }
In the above program, we have first created the array arr[] and then we pass this array to the function getarray(). The getarray() function prints all the elements of the array arr[].

Output

Passing array to a function as a pointer
Now, we will see how to pass an array to a function as a pointer. 
        
            #include   
                void printarray(char *arr)  
                {  
                    printf("Elements of array are : ");  
                    for(int i=0;i<5;i++)  
                    {  
                        printf("%c ", arr[i]);  
                    }  
                }  
                int main()  
                {  
                  char arr[5]={'A','B','C','D','E'};  
                  printarray(arr);  
                  return 0;  
                }
In the above code, we have passed the array to the function as a pointer. The function printarray() prints the elements of an array.

Output

How to return an array from a function
Returning pointer pointing to the array 
            
                #include   
                    int *getarray()  
                    {  
                        int arr[5];  
                        printf("Enter the elements in an array : ");  
                        for(int i=0;i<5;i++)  
                        {  
                            scanf("%d", &arr[i]);  
                        }  
                        return arr;  
                    }  
                    int main()  
                    {  
                      int *n;  
                      n=getarray();  
                      printf("nElements of array are :");  
                      for(int i=0;i<5;i++)  
                        {  
                            printf("%d", n[i]);  
                        }  
                        return 0;  
                    }
In the above program, getarray() function returns a variable 'arr'. It returns a local variable, but it is an illegal memory location to be returned, which is allocated within a function in the stack. Since the program control comes back to the main() function, and all the variables in a stack are freed. Therefore, we can say that this program is returning memory location, which is already de-allocated, so the output of the program is a segmentation fault.

Output

There are three right ways of returning an array to a function: Returning array by passing an array which is to be returned as a parameter to the function. 
        
            #include   
                int *getarray(int *a)  
                {  
                    
                    printf("Enter the elements in an array : ");  
                    for(int i=0;i<5;i++)  
                    {  
                        scanf("%d", &a[i]);  
                    }  
                    return a;  
                }  
                int main()  
                {  
                  int *n;  
                  int a[5];  
                  n=getarray(a);  
                  printf("nElements of array are :");  
                  for(int i=0;i<5;i++)  
                    {  
                        printf("%d", n[i]);  
                    }  
                    return 0;  
                }

Output

Returning array using malloc() function. 
        
            #include   
                #include  
                int *getarray()  
                {  
                    int size;  
                    printf("Enter the size of the array : ");  
                    scanf("%d",&size);  
                    int *p= malloc(sizeof(size));  
                    printf("nEnter the elements in an array");  
                    for(int i=0;i

Output

Using Static Variable 
    
        #include   
            int *getarray()  
            {  
              static int arr[7];  
              printf("Enter the elements in an array : ");  
              for(int i=0;i<7;i++)  
              {  
                  scanf("%d",&arr[i]);  
              }  
              return arr;  
                  
            }  
            int main()  
            {  
              int *ptr;  
              ptr=getarray();  
              printf("nElements that you have entered are :");  
              for(int i=0;i<7;i++)  
              {  
                  printf("%d ", ptr[i]);  
              }  
            }

Output

In the above code, we have created the variable arr[] as static in getarray() function, which is available throughout the program. Therefore, the function getarray() returns the actual memory location of the variable 'arr'.

Using Structure

The structure is a user-defined data type that can contain a collection of items of different types. Now, we will create a program that returns an array by using structure. 
        
            #include   
                #include  
                struct array  
                {  
                    int arr[8];  
                };  
                struct array getarray()  
                {  
                    struct array y;  
                    printf("Enter the elements in an array : ");  
                    for(int i=0;i<8;i++)  
                    {  
                        scanf("%d",&y.arr[i]);  
                    }  
                    return y;  
                }  
                int main()  
                {  
                  struct array x=getarray();  
                  printf("Elements that you have entered are :");  
                  for(int i=0;x.arr[i]!='0';i++)  
                  {  
                      printf("%d ", x.arr[i]);  
                  }  
                    return 0;  
                }

Output