ArrayList.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include "ArrayList.h"

//create a new list with a initial capacity
ArrayList* createArrayList(int capacity) {
    ArrayList* list = malloc(sizeof(ArrayList));
    if (list == NULL) {
        fprintf(stderr, "unable to allocate memory\n");
        exit(1);
    }

    list->arr = malloc(capacity * sizeof(void*));
    if (list->arr == NULL) {
        fprintf(stderr, "unable to allocate memory\n");
        free(list);
        exit(1);
    }

    list->size = 0;
    list->capacity = capacity;
    return list;
}

//add element to list
void addToArrayList(ArrayList* list, void* val) {
    if (list->size == list->capacity) { //if at capacity double capacity of list
        void** newArr = realloc(list->arr, list->capacity * 2 * sizeof(void*));
        if (newArr == NULL) {
            fprintf(stderr, "unable to allocate memory\n");
            exit(1);
        }
        list->arr = newArr;
        list->capacity *= 2;
    }
    list->arr[list->size] = val; //assign element
    list->size++;
}

//remove element at index and shift elements left
void removeFromArrayList(ArrayList* list, int idx) {
    if (idx < 0 || idx >= list->size) {
        fprintf(stderr, "index out of bounds\n");
        exit(1);
    }

    //shift elements left to fill the gap
    for (int i = idx; i < list->size - 1; i++) {
        list->arr[i] = list->arr[i + 1];
    }

    list->size--;

    //reduce capacity if too much unused space
    if (list->size > 0 && list->size <= list->capacity / 4) {
        void** newArr = realloc(list->arr, (list->capacity / 2) * sizeof(void*));
        if (newArr != NULL) { //only shrink if realloc succeeds
            list->arr = newArr;
            list->capacity /= 2;
        }
    }
}


//return element at index
void* getFromArrayList(ArrayList* list, int idx) {
    if (idx < 0 || idx >= list->size) {
        fprintf(stderr, "index out of bounds\n");
        exit(1);
    }
    return list->arr[idx];
}

//set element at index
void setArrayList(ArrayList* list, int idx, int val) {
    if (idx < 0 || idx >= list->size) {
        fprintf(stderr, "index out of bounds\n");
        exit(1);
    }
    list->arr[idx] = (void*)(intptr_t)val;
}

//free list
void freeArrayList(ArrayList* list) {
    if (list != NULL) {
        free(list->arr);
        free(list);
    }
}