c++ replacing order of items in byte array - c++

Question

I'm writing a code for Arduino C++.
I have a byte array with hex byte values, for example:
20 32 36 20 E0 EC 20 F9 F0 E9 E9 E3 F8 5C 70 5C 70 5C 73 20 E3 E2 EC 20 F8 E0 E5 E1 EF 20 39 31 5C
There are four ASCII digits in these bytes:
HEX 0x32 is number 2 in ascii code
HEX 0x35 is number 5 in ascii code
HEX 0x39 is number 9 in ascii code
and so on....
https://www.ascii-codes.com/cp862.html
So the hex values 32, 36 represent the number 26, and 39, 31 represent 91.
I want to find these numbers and reverse each group, so that (in this example) 62 and 19 are represented instead of 26 and 91.
The output would thus have to look like this:
20 36 32 20 E0 EC 20 F9 F0 E9 E9 E3 F8 5C 70 5C 70 5C 73 20 E3 E2 EC 20 F8 E0 E5 E1 EF 20 31 39 5C
The numbers don't have to be two digits but could be anything in 0-1000
I also know that each group of such numbers is preceded by the hex value 20, if that helps.
I have done this in C# (with some help of Stack overflow users :-) ):
string result = Regex.Replace(HexMessage1,
#"(?<=20\-)3[0-9](\-3[0-9])*(?=\-20)",
match => string.Join("-", Transform(match.Value.Split('-'))));
private static IEnumerable<string> Transform(string[] items)
{
// Either terse Linq:
// return items.Reverse();
// Or good old for loop:
string[] result = new string[items.Length];
for (int i = 0; i < items.Length; ++i)
result[i] = items[items.Length - i - 1];
return result;
}
Can someone help me make it work on C++?

Answer 1

Loop over the array, element by element, looking for 0x32 or 0x39. If found, check the next byte (if within bounds) to see if it matches 0x36 or 0x31 (respectively). If it does then swap the current and the next byte. Continue the loop, skipping over the current and the next byte.