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

#define MAX_N 1000000

unsigned char b[MAX_N / 4];

int get(int i) {
  return (b[i/4] >> (2 * (i % 4))) & 3;
}

void set(int i, int x) {
  // Clear the previous value if needed
  b[i/4] &= ~(3 << (2 * (i % 4)));
  b[i/4] ^= x << (2 * (i % 4));
}

int main(void) {
  srand(time(NULL));

  int v[MAX_N]; // For testing

  // Fill the bitset with junk
  for (int i = 0; i < MAX_N / 4; i++) {
    b[i] = rand() % 256;
  }

  // Set random values in both arrays
  for (int i = 0; i < MAX_N; i++) {
    v[i] = rand() % 4;
    set(i, v[i]);
  }

  // Assert that the arrays contain equal values
  for (int i = 0; i < MAX_N; i++) {
    assert(get(i) == v[i]);
  }
}