23. Binary to string conversion

Write a function that, given a range of 8-bit integers (such as an array or vector), returns a string that contains a hexadecimal representation of the input data. The function should be able to produce both uppercase and lowercase content. Here are some input and output examples:

Input: { 0xBA, 0xAD, 0xF0, 0x0D }, output: "BAADF00D" or "baadf00d"
Input: { 1,2,3,4,5,6 }, output: "010203040506"