<Codesignal> Array Packing

Medium

You are given an array of up to four non-negative integers, each less than 256.

Your task is to pack these integers into one number M in the following way:

• The first element of the array occupies the first 8 bits of M;
• The second element occupies next 8 bits, and so on.

Return the obtained integer M.

Note: the phrase "first bits of M" refers to the least significant bits of M - the right-most bits of an integer. For further clarification see the following example.

Example

For a = [24, 85, 0], the output should be
arrayPacking(a) = 21784.

An array [24, 85, 0] looks like [00011000, 01010101, 00000000] in binary.
After packing these into one number we get 00000000 01010101 00011000 (spaces are placed for convenience), which equals to 21784.

Input/Output

• [execution time limit] 0.5 seconds (c)

• [input] array.integer a

  Guaranteed constraints:
  1 ≤ a.length ≤ 4,
  0 ≤ a[i] < 256.

• [output] integer

[C] Syntax Tips

// Prints help message to the console
// Returns a string
char * helloWorld(char * name) {
    char * answer = malloc(strlen(name) + 8);
    printf("This prints to the console when you Run Tests");
    strcpy(answer, "Hello, ");
    strcat(answer, name);
    return answer;
}

---

Solution

// Arrays are already defined with this interface:
// typedef struct arr_##name {
//   int size;
//   type *arr;
// } arr_##name;
//
// arr_##name alloc_arr_##name(int len) {
//   arr_##name a = {len, len > 0 ? malloc(sizeof(type) * len) : NULL};
//   return a;
// }
//
//
int arrayPacking(arr_integer a)
{
	int M=0;

	for(int i=0;i<a.size;i++)
		M+=a.arr[i]<<i*8;

	return M;
}