#include <stdio.h>
#include <stdlib.h>
// A struct that stores:
// 1. A pointer to a dynamically allocated array
// 2. The number of elements currently used
// 3. The total allocated capacity
typedef struct {
int *data; // Pointer to the array in heap memory
size_t size; // Number of valid elements
size_t capacity; // Total allocated space
} IntArray;
// Initialize the dynamic array with a given starting capacity
void initArray(IntArray *arr, size_t initial_capacity) {
// Allocate memory for 'initial_capacity' integers
arr->data = malloc(initial_capacity * sizeof(int));
// Always check if malloc succeeded
if (arr->data == NULL) {
perror("malloc failed");
exit(EXIT_FAILURE);
}
arr->size = 0; // No elements yet
arr->capacity = initial_capacity; // Store allocated capacity
}
// Add a new element to the array, resizing if needed
void pushBack(IntArray *arr, int value) {
// If array is full, grow it
if (arr->size == arr->capacity) {
// Double the capacity for efficiency
arr->capacity *= 2;
// Reallocate memory to the new size
int *newData = realloc(arr->data, arr->capacity * sizeof(int));
// Check if realloc succeeded
if (newData == NULL) {
perror("realloc failed");
exit(EXIT_FAILURE);
}
arr->data = newData; // Update pointer
}
// Store the new value and increase size
arr->data[arr->size] = value;
arr->size++;
}
// Free the allocated memory and reset metadata
void freeArray(IntArray *arr) {
free(arr->data); // Release heap memory
arr->data = NULL; // Avoid dangling pointer
arr->size = 0;
arr->capacity = 0;
}
int main() {
IntArray arr;
// Create array with initial capacity of 6
initArray(&arr, 6);
// Add some values
pushBack(&arr, 7);
pushBack(&arr, 19);
pushBack(&arr, 3);
pushBack(&arr, 87);
// Print stored values
for (size_t i = 0; i < arr.size; i++) {
printf("%d\n", arr.data[i]);
}
printf("arr.size = %d\n", arr.size);
printf("arr.capacity = %d\n", arr.capacity);
// Clean up memory
freeArray(&arr);
return 0;
}
/*
run:
7
19
3
87
arr.size = 4
arr.capacity = 6
*/
