// A program that takes in an array of a given length and swaps the first and 
// the last elements of that array. 
// Sasha Vassar Week 5, Lecture 9


#include <stdio.h>

// PROBLEM: Read in an array of numbers (user will specify how many numbers 
// they plan to read in). Then  the first number and the last number in the 
// array will be swapped, and the modified array printed out again.
// How shall we solve this?
// 1. Read in numbers
//     - User specifies how many numbers they will enter
//     - User then provides the numbers
// 2. Print out the original array
// 3. Swap the first and the last number in the array
// 4. Print out the modified array


#define MAX_SIZE 100

void print(int array[], int size);
int read_size(int array[]);
void swap(int *number1_ptr, int *number2_ptr);

int main (void) {

    //Declare an array
    int array[MAX_SIZE];
    //Find out size of the array, by calling the function read_size(array)
    int size = read_size(array);
    
    //Print out original array, by calling the function print
    printf("The original array is:\n");
    print(array, size);
    //Swap the first and the last element of the array, by calling the function 
    //swap. Notice that swapping is best done with pointers to the specific 
    //array indexes.
    swap(&array[0], &array[size-1]);
    
    //Print out modified array, by calling the function print again
    printf("The array with the first and last numbers swapped is:\n");
    print(array, size);

    return 0;
}

int read_size(int array[]) {
    int counter = 0;
    printf("How many numbers would you like to enter? ");
    scanf("%d", &counter);
    int i = 0;
    while (i < counter) {
        printf("Enter a number for the array: ");
        scanf("%d", &array[i]);
        i++;
    }    
    return counter;
}

// 1, 2, 3, 4, 5
// *1, *5
void swap(int *number1_ptr, int *number2_ptr) {
    // temp = 1
    int temp = *number1_ptr;
    //address at pointer 1 = 5
    *number1_ptr = *number2_ptr;
    //address at pointer 2  = 1
    *number2_ptr = temp;
}

void print(int array[], int size) {
    int i = 0;
    while (i < size) {
        printf("%d ", array[i]);
        i++;
    }
    printf("\n");
}