Assignment 2 - Intro CS

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


/* Execution Functions declarations */
void Ex1();
void Ex2();
void Ex3();
void Ex4();
void Ex5();

/* Declarations of other functions */

int replace_couple(int n); // 1
int increase_decrease(int n, int f); // 2
int index_three_minus_all(); // 3
int k_palindrome(int* arr, int k, int n); // 4
int* min_of_arr(int* a, int n, int k, int* p);


int main()
{
    int select = 0, i, all_Ex_in_loop = 0;
    printf("Run menu once or cyclically?\n(Once - enter 0, cyclically - enter other number) ");
    if (scanf_s("%d", &all_Ex_in_loop) == 1)
        do
        {
            for (i = 1; i <= 5; i++)
                printf("Ex%d--->%d\n", i, i);
            printf("EXIT-->0\n");
            do {
                select = 0;
                printf("please select 0-5 : ");
                scanf_s("%d", &select);
            } while ((select < 0) || (select > 5));
            switch (select)
            {
                case 1: Ex1(); break;
                case 2: Ex2(); break;
                case 3: Ex3(); break;
                case 4: Ex4(); break;
                case 5: Ex5(); break;
            }
        } while (all_Ex_in_loop && select);
        return 0;
}


// Function 1
int replace_couple(int n)
{
    // 123456 - 214365
    // 1234567 - 1325476

    int curr_num, prev_num;
    int new_num;

    curr_num = n % 10; // 5
    prev_num = (n / 10) % 10; // 6

    new_num = (curr_num * 10) + prev_num;

    if (n < 100 && n > 9) // Even > 10 --- 100
        return new_num;

    if (n < 10)
        return curr_num;


    return replace_couple(n / 100) * 100 + new_num;

}

// Function 2
int increase_decrease(int n, int f)
{
    switch (f)
    {
        case 0:
        {
            // f = 0 Start
            int curr_num, prev_num;

            if (n < 10)
                return 1;

            curr_num = n % 10;
            prev_num = (n / 10) % 10;

            if (prev_num > curr_num)
                return increase_decrease(n / 10, 0);

            return 0;
            // End of f = 0 Stop
        }

        case 1:
        {
            // For f = 1 Start

            int curr_num, prev_num;

            if (n < 10)
                return 1;

            curr_num = n % 10;
            prev_num = (n / 10) % 10;

            if (curr_num > prev_num)
                return increase_decrease(n / 10, 1);

            return 0;
            // End of f = 0 Stop
        }

        case 2:
        {
            // For f = 2 Start
            int curr_num, prev_num;

            curr_num = n % 10;
            prev_num = (n / 10) % 10;

            if (prev_num > curr_num) // 12341
                return increase_decrease(n / 10, 4);

            else
                return 0;

            // End of f = 2 Stop
        }

        case 3: //
        {
            int curr_num, prev_num;

            curr_num = n % 10;
            prev_num = (n / 10) % 10; //  432123

            if (prev_num < curr_num)
                return increase_decrease(n / 10, 5);

            else
                return 0;
        }

        case 4:
        {
            int curr_num, prev_num;

            if (n < 10)
                return 0;

            curr_num = n % 10;
            prev_num = (n / 10) % 10;

            if (prev_num > curr_num) // 123421
                return increase_decrease(n / 10, 4);

            if (prev_num < curr_num)
                return increase_decrease(n / 10, 1);
        }

        case 5:
        {
            int curr_num, prev_num;

            if (n < 10)
                return 0;

            curr_num = n % 10;
            prev_num = (n / 10) % 10;

            if (prev_num < curr_num) // 432123
                return increase_decrease(n / 10, 5);

            if (prev_num > curr_num)
                return increase_decrease(n / 10, 0);
        }
    } // end of switch
}

// Function 3
int index_three_minus_all()
{
    int sum_by_three = 0;
    int all_except_three = 0;

    for (int i = 1; i <= 3; i++)
    {
        int curr_num;

        printf("Enter num: ");
        scanf_s("%d", &curr_num);

        if (i == 3 && curr_num != -1)
        {
            sum_by_three = curr_num;
            all_except_three += 0;
        }

        else
        {
            if (curr_num == -1)
                all_except_three += 0;
            else
                all_except_three += curr_num;
        }

        if (curr_num == -1)
            return (sum_by_three - all_except_three);
    }

    int result = sum_by_three - all_except_three;

    return result + index_three_minus_all();
}

// Function 4
int k_palindrome(int* arr, int k, int n)
{
    // 10,20,3,6,1,16,3,14,2,7,25,5
    // 0  1  2 3 4 5  6  7 8 9 10 11
    // n = 12

    if (n < 2 * k)
        return 1;

    int left = 0, right = 0;

    for (int i = 0; i < k; i++)
    {
        left += arr[i];
    }

    for (int j = n - 1; j >= n - k; j--)
    {
        right += arr[j];
    }

    if (left == right)
        return k_palindrome(arr + k, k, n - (2 * k));

    else
        return 0;

}

// Function 5
int* min_of_arr(int* a, int n, int k, int* p)
{

    int* b;
    b = (int*)malloc(k * sizeof(int));

    // [10,5,2,60,2,7,2,10]

    int min_value, min_index;
    int max_value;

    int sum_b = 0;

    for (int i = 0; i < k; i++) // 4
    {
        min_value = a[0];
        min_index = 0;

        max_value = a[0];

        for (int j = 1; j < n; j++) // 8
        {
            if (max_value <= a[j])
                max_value = a[j]; // 60

            if (min_value >= a[j])
            {
                min_value = a[j]; // 2
                min_index = j; // 6
            }
        }

        a[min_index] = max_value;

        sum_b += min_value;
        b[i] = min_value;
    }

    *p = sum_b;
    return b;
}


// Execution Functions
/*.............................*/
void Ex1()
{   //  This function will return a new number with reversed
    // couple of numbers

    int num;

    printf("\nThis function will flip every couple of numbers\nof the original number.\n");
    printf("\nEnter an integer: ");
    scanf_s("%d", &num);
    printf("\nThe new number is: %d\n\n", replace_couple(num));
}

/*.............................*/
void Ex2()
{
    int num;
    int f;

    printf("\nThis function will return '1' if true and '0' if false,\ndepending on the function.\n");
    printf("\nFunction:\n");
    printf("\n0: Right-To-Left; Number is extremely increasing.");
    printf("\n1: Right-To-Left; Number is extremely decreasing.");
    printf("\n2: Right-To-Left; Number is extremely increasing and then extremely decreasing.");
    printf("\n3: Right-To-Left; Number is extremely decreasing and then extremely increasing.\n");

    printf("\nEnter function: ");
    scanf_s("%d", &f);

    printf("\nEnter number: ");
    scanf_s("%d", &num);

    printf("\nResult is: %d\n\n", increase_decrease(num, f));
}

/*.............................*/
void Ex3()
{
    printf("\nThis function will print the sum of every number in index number that divides by 3,\n minus all the rest of the numbers.\n");
    printf("\nEnter numbers and input -1 to stop running..\n");

    int result = index_three_minus_all();

    printf("\nResult is: %d\n\n", result);
}

/*.............................*/
void Ex4()
{
    int n, k;
    int* arr;

    printf("\nThis function will get an array and show if there is a palindrome in the array.\n'1' = True, '0' = False\n");
    printf("\nIt can check if a sum of 'k' numbers is the same of the sum of 'k' numbers in the other side.\n");

    printf("Enter k: ");
    scanf_s("%d", &k);

    printf("Enter quantity of numbers: ");
    scanf_s("%d", &n);

    arr = (int*)malloc(n * sizeof(int));

    for (int i = 0; i < n; i++)
    {
        printf("Enter num %d/%d: ", i + 1, n);
        scanf_s("%d", (arr + i));
    }

    printf("\n\n");

    int result = k_palindrome(arr, k, n);

    printf("\nResult is: %d\n", result);

    free(arr);
}

/*.............................*/
void Ex5()
{
    int n, k;
    int* a;

    int* b; // new array
    int p; // sum of new array

    printf("\nThis function will show the smallest numbers in a sequence of numbers and will also print their sum.\n");

    printf("\nHow many numbers would you like to view?: ");
    scanf_s("%d", &k);

    printf("Enter quantity of numbers in the sequence: ");
    scanf_s("%d", &n);

    a = (int*)malloc(n * sizeof(int));

    for (int i = 0; i < n; i++)
    {
        printf("Enter num %d/%d: ", i + 1, n);
        scanf_s("%d", (a + i));
    }

    b = min_of_arr(a, n, k, &p);

    for (int j = 0; j < k; j++)
    {
        printf("%d   ", b[j]);
    }

    printf("\nSum: %d\n", p);

    free(a);
    free(b);
}