Move all values inside vectors in C - c

Question

i'm writing a code for a project, in which i need to move values inside a vector! For example, i have a completely "null" vector:
[0][0][0][0][0]
Then i will add a value to it's first position: [10][0][0][0][0]!
Ok, now i need to add again a value to the first position, but i cant lose the value already there, i want to move it to the right, like:
[0][10][0][0][0]
To put the new one there: [5][10][0][0][0]
And then do this again, move the 5 and the 10 to the right again, to add a new one in the first, and so on!
I hope i was clear enough!
#EDIT :
Its done guys! Thanks to everyone that tried to help!
The problem was solved using #AkashPradhan function:
void changeposition(int* vetor, unsigned int size, int valor)
{
unsigned int i = size - 1;
for(; i > 0; --i)
vetor[i] = vetor[i-1] ;
vetor[0] = valor ;
}
Thanks #AkashPradhan! The function worked perfectly with my code!

Answer 1

You can use a Linked List and add to the front node or you could use an array and shift the elements by one position for each insertion.
In this case, I would recommend using a Linked List as the insertion routine will not involving moving every element. However if frequent random access to elements in required, use the array approach.
void insert_front(int* array, unsigned int size, int value)
{
unsigned int i = size - 1;
for(; i > 0; --i)
array[i] = array[i-1] ;
array[0] = value ;
}
Note that the routine does not check if you are inserting more elements that the size of the array.

Answer 2

You could implement this as a ring buffer, in which case you don't need to copy the elements all the time. An example of it would be:
typedef struct
{
size_t bufferSize;
size_t currentPos;
int *data;
} ring_buffer;
void init_buffer(ring_buffer *buffer, size_t N)
{
buffer->bufferSize = N;
buffer->currentPos = 0;
buffer->data = malloc(N*sizeof(int));
}
void free_buffer(ring_buffer *buffer)
{
free(buffer->data);
}
void push_buffer(ring_buffer *buffer, int value)
{
++buffer->currentPos;
if (buffer->currentPos >= buffer->bufferSize)
buffer->currentPos = 0;
buffer->data[buffer->currentPos] = value;
}
int get_buffer(ring_buffer *buffer, size_t pos)
{
size_t dataPos = buffer->currentPos + pos;
if (dataPos >= buffer->bufferSize)
dataPos -= buffer->bufferSize;
return buffer->data[dataPos];
}
or you could use a linked list as suggested by #AkashPradhan.

Answer 3

Define your own array, implement push operation, shift right data when push a new element. This implementation would delete the stale element.
typedef struct Array {
int *data;
size_t len; // current size of the array
size_t cap; // capacity of the array
}Array;
Array * new_array (size_t cap_){
Array *arr = (Array *)malloc(sizeof(Array));
arr->cap = cap_;
arr->len = 0;
arr->data = (int*)malloc(sizeof(int) * cap);
return arr;
}
void free_array(Array * arr){
if (arr->data != NULL)
free(arr->data);
free(arr);
}
void push(int x, Array *arr) {
int ptr = std::min(len, cap) - 2;
for(int i = ptr;i >= 0;i --) {
arr->data[ptr + 1] = arr->data[ptr];
}
arr->data[0] = x;
len = std::max(cap, len + 1);
}
Update : You can also use Tamás Szabó 's answer to avoid data movement.

Answer 4

If you need to write the corresponding function yourself then it can look the following way
size_t move( int a[], size_t n )
{
if ( n++ != 0 )
{
for ( size_t i = n; --i != 0; ) a[i] = a[i-1];
}
return n;
}
And you could use it the following way
size_t n = 0;
n = move( a, n );
a[0] = 10;
n = move( a, n );
a[0] = 5;
for ( size_t i = 0; i < n; i++ ) printf( "%d ", a[i] );
printf( "\n" );
Otherwise you have to use standard C function memmove the following way
memmove( a + 1, a, n * sizeof( int ) );
++n;
where n is the current number of actual elements in the array.