【数据结构】C语言实现动态扩容数组

// resizable array

/*
Think about a set of functions that provide a mechanism of resizable array of int.
    • Growable
    • Get the current size
    • Access to the elements
*/

/*
the Interface
    • Array array_create(int init_size);
    • void array_free(Array *a);
    • int array_size(const Array *a);
    • int* array_at(Array *a, int index);
    • void array_inflate(Array *a, int more_size);
*/

typedef struct
{
    int* array;
    int size;
} Array;

#define BLOCK_SIZE 16

Array array_create(int init_size)
{
    Array a;
    a.array = (int*)malloc(sizeof(int) * init_size);
    a.size = init_size;
    return a;
}

void array_free(Array *a)
{
    free(a->array);
    a->size = 0;
}

int array_size(const Array *a)
{
    return a->size;
}

void array_inflate(Array *a, int more_size)
{
    int* p = (int*)malloc(sizeof(int) * (a->size + more_size));
    for ( int i=0; i<a->size; i++ )
    {
        p[i] = a->array[i];
    }
    free(a->array);
    a->array = p;
    a->size = a->size + more_size;
}

void array_inflate(Array *a, int more_size)
{
    int* p = (int*)malloc(sizeof(int) * (a->size + more_size));
    memcpy((void*) p, (void*) a->array, a->size*sizeof(int));
    free(a->array);
    a->array = p; a->size = a->size+more_size;
}

int* array_at(Array *a, int index)
{
    if ( index >= a->size )
    {
        array_inflate(a,
            (index/BLOCK_SIZE+1) * BLOCK_SIZE-a->size);
    }
    return &(a->array[index]);
}

int test()
{
    // use array_at()
    Array a = array_create(10);
    *(array_at(&a, 5)) = 6;
    *(array_at(&a, 10)) = *(array_at(&a, 5));
}

/*
will it be better
    • to have two access functions:
    • array_get(), and
    • array_set()

Array a = array_create(10);
array_set(&a, 5, 6);
array_set(&a, 10, array_get(&a, 5));
*/

未完待续，后续补充链式分块扩容数组（二维数组），以及C++ Vector实现

参考：C语言进阶- 浙江大学Mooc