Arrays

#include <stdio.h>

// Function to reverse an array
void reverseArray(int arr[], int size) {
    int start = 0, end = size - 1;
    while (start < end) {
        // Swap the elements
        int temp = arr[start];
        arr[start] = arr[end];
        arr[end] = temp;
        start++;
        end--;
    }
}

// Function to count the number of positive integers in an array
int countPositive(int arr[], int size) {
    int count = 0;
    for (int i = 0; i < size; i++) {
        if (arr[i] > 0) {
            count++;
        }
    }
    return count;
}

int main() {
    // Problem 1: Create an array of 10 numbers and verify (ptr+2) points to the third element
    int arr[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    int *ptr = arr;
    printf("Problem 1: Pointer arithmetic verification:\n");
    printf("First element: %d\n", *ptr);
    printf("Third element using (ptr+2): %d\n\n", *(ptr + 2)); // This will print the 3rd element

    // Problem 2: If S[3] is a 1-D array of integers, *(S+3) refers to the third element
    printf("Problem 2: *(S+3) refers to the third element? Answer: True\n\n");

    // Problem 3: Create an array of 10 integers and store a multiplication table of 5
    int table5[10];
    printf("Problem 3: Multiplication table of 5:\n");
    for (int i = 0; i < 10; i++) {
        table5[i] = 5 * (i + 1);
        printf("%d ", table5[i]);
    }
    printf("\n\n");

    // Problem 4: Repeat Problem 3 for a general input provided by the user using scanf
    int n;
    printf("Problem 4: Enter a number to generate its multiplication table: ");
    scanf("%d", &n);
    int tableN[10];
    for (int i = 0; i < 10; i++) {
        tableN[i] = n * (i + 1);
        printf("%d ", tableN[i]);
    }
    printf("\n\n");

    // Problem 5: Reverse an array
    printf("Problem 5: Reversing the array from Problem 3:\n");
    reverseArray(table5, 10);
    for (int i = 0; i < 10; i++) {
        printf("%d ", table5[i]);
    }
    printf("\n\n");

    // Problem 6: Count the number of positive integers in an array
    int mixedArr[10] = {-1, 4, -3, 7, 8, -5, 6, -9, 2, -6};
    printf("Problem 6: Counting the positive integers in mixedArr:\n");
    int positiveCount = countPositive(mixedArr, 10);
    printf("Number of positive integers: %d\n\n", positiveCount);

    // Problem 7: Create a 3x10 array containing multiplication tables of 2, 7, and 9
    int tables[3][10];
    printf("Problem 7: Multiplication tables of 2, 7, and 9:\n");
    for (int i = 0; i < 10; i++) {
        tables[0][i] = 2 * (i + 1);
        tables[1][i] = 7 * (i + 1);
        tables[2][i] = 9 * (i + 1);
    }
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 10; j++) {
            printf("%d ", tables[i][j]);
        }
        printf("\n");
    }
    printf("\n");

    // Problem 8: Repeat Problem 7 for a custom input given by the user
    int m1, m2, m3;
    printf("Problem 8: Enter three numbers for custom multiplication tables: ");
    scanf("%d %d %d", &m1, &m2, &m3);
    int customTables[3][10];
    for (int i = 0; i < 10; i++) {
        customTables[0][i] = m1 * (i + 1);
        customTables[1][i] = m2 * (i + 1);
        customTables[2][i] = m3 * (i + 1);
    }
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 10; j++) {
            printf("%d ", customTables[i][j]);
        }
        printf("\n");
    }
    printf("\n");

    // Problem 9: Create a three-dimensional array and print the address of its elements in increasing order
    int arr3D[2][2][2] = {{{1, 2}, {3, 4}}, {{5, 6}, {7, 8}}};
    printf("Problem 9: Addresses of 3D array elements in increasing order:\n");
    for (int i = 0; i < 2; i++) {
        for (int j = 0; j < 2; j++) {
            for (int k = 0; k < 2; k++) {
                printf("Address of arr3D[%d][%d][%d]: %p\n", i, j, k, &arr3D[i][j][k]);
            }
        }
    }

    return 0;
}