Dynamic Array

Dynamic.c

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

// Define a structure for DynamicArray
typedef struct {
    int *data;      // Pointer to the array of elements
    int size;       // Number of elements currently in the array
    int capacity;   // Total capacity (allocated memory) of the array
} DynamicArray;

// Function to create a new dynamic array with an initial capacity
DynamicArray* create_array(int initial_capacity) {
    // Allocate memory for the DynamicArray structure
    DynamicArray* arr = malloc(sizeof(DynamicArray));
    
    // Allocate memory for the data array with the specified capacity
    arr->data = malloc(initial_capacity * sizeof(int));
    
    // Initialize size to 0 and set the capacity to the provided value
    arr->size = 0;
    arr->capacity = initial_capacity;
    
    return arr;
}

// Function to resize the array to a new capacity
void resize(DynamicArray* arr, int new_capacity) {
    // Reallocate memory for the data array with the new capacity
    arr->data = realloc(arr->data, new_capacity * sizeof(int));
    
    // Update the capacity field
    arr->capacity = new_capacity;
}

// Function to add a new element to the dynamic array
void push(DynamicArray* arr, int value) {
    // Check if the array is full (size == capacity)
    if (arr->size == arr->capacity) {
        // Double the capacity of the array if full
        resize(arr, arr->capacity * 2);
    }
    
    // Add the new value to the array and increment the size
    arr->data[arr->size++] = value;
}

// Function to remove the last element from the dynamic array
void pop(DynamicArray* arr) {
    // Ensure the array is not empty
    if (arr->size == 0) return;
    
    // Decrement the size of the array (removing the last element)
    arr->size--;
    
    // Check if the array size is less than or equal to 30% of its capacity
    // and if the current capacity is more than 1 (to avoid shrinking to zero)
    if (arr->size <= arr->capacity * 0.3 && arr->capacity > 1) {
        // Halve the capacity of the array if the size is small enough
        int new_capacity = arr->capacity / 2;
        
        // Ensure the new capacity is at least 1
        if (new_capacity < 1) new_capacity = 1;
        
        // Resize the array to the new, smaller capacity
        resize(arr, new_capacity);
    }
}

// Function to free the memory allocated for the dynamic array
void free_array(DynamicArray* arr) {
    // Free the memory allocated for the data array
    free(arr->data);
    
    // Free the memory allocated for the DynamicArray structure itself
    free(arr);
}

// Function to print the elements in the dynamic array (for testing)
void print_array(DynamicArray* arr) {
    printf("Array (size: %d, capacity: %d): ", arr->size, arr->capacity);
    
    // Print each element in the array
    for (int i = 0; i < arr->size; i++) {
        printf("%d ", arr->data[i]);
    }
    printf("\n");
}

// Example usage of the dynamic array
int main() {
    // Create a dynamic array with an initial capacity of 4
    DynamicArray* arr = create_array(4);
    
    // Add elements to the array (this will cause resizing)
    for (int i = 0; i < 20; i++) {
        push(arr, i);   // Add the number i to the array
        print_array(arr);  // Print the current state of the array
    }

    // Remove elements from the array (this will cause shrinking)
    for (int i = 0; i < 18; i++) {
        pop(arr);   // Remove the last element from the array
        print_array(arr);  // Print the current state of the array
    }

    // Free the memory when done
    free_array(arr);
    
    return 0;
}