C

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

int main()
{
	unsigned int n = 20;
	int* source = (int*)malloc(n * sizeof(int));

	srand(1);
	for (unsigned int i = 0; i < n; ++i)
	{
		source[i] = rand() % 2;
	}

	unsigned int k = (n + 7) / 8;
	uint8_t* compressed = (uint8_t*)calloc(k, sizeof(uint8_t));

	unsigned int i_n = 0;
	for (unsigned int i = 0; i < k; ++i)
	{
		for (int j = 7; j >= 0 && i_n < n; --j, ++i_n)
		{
			if (source[i_n])
			{
				compressed[i] |= source[i_n] << j;
			}
		}
	}

	for (unsigned int i = 0; i < n; ++i)
	{
		printf("%d", source[i]);
	}

	printf("\n");

	for (unsigned int i = 0; i < k; ++i)
	{
		for (int j = 7; j >= 0; --j)
		{
			printf("%d", (compressed[i] & (1 << j)) ? 1 : 0);
		}
	}

	free(compressed);
	free(source);
}