array_packing.py

def solution(a):

    out = 0
    for i in range(len(a)):

        out += a[i] << 8 * i
    return out


print(solution([24, 85, 0]))
# [00011000, 01010101, 00000000]
# Expected Output: 21784

# print(solution([23, 45, 39]))
# Expected Output: 2567447


# 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
    # solution(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] 4 seconds (py3)

    # [input] array.integer a

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

    # [output] integer