use a temporary variable

int Array1[] = {1, 4, 67};

int tmp = Array1[0];
Array1[0] = Array1[1];
Array1[1] = Array1[2];
Array1[2] = tmp; // old Array1[0]

To start with the basics…

Suppose the following array:

int a[5] = {1, 2, 3, 4, 5};

Now we want to swap numbers between them (for this example i’ll swap 1 with 5). You can make this on spot:

int aux = a[5];
a[5] = a[1];
a[1] = aux;

To have it nicelly you can make it into a function:

void swap_int(int* a, int* b)
{
    int aux = *a;
    *a = *b;
    *b = aux;
}

And with this function you can call swap_int(&v[1], &v[5]); and will produce the same result.

Use the swap function as below:

#include<stdio.h>
#include<stdlib.h>

void swap(int *a, int *b);

int main() {
        int a[3] = {1,4,67};

        for(int i = 0; i < 3; i++)
                printf("%d ", a[i]);
        printf("n");

        swap(a, a + 2);
        swap(a, a + 1);

        for(int i = 0; i < 3; i++)
                printf("%d ", a[i]);
        printf("n");
}

void swap(int *a, int *b) {
        int aux = *a;
        *a = *b;
        *b = aux;
}