We can't tell you - we don't have access to your data, so we can't try your code under exactly the same conditions you can - and this is almost certainly going to be data related.
But this in your first
else if((cd[i]>2) && (cd[i+1]<9))
Should probably look like this in your second:
else if((cd[i]>'2') && (cd[i+1]<'9'))
That won't fix your problem though!
Probably though, you are running off the end of your array
So, it's going to be up to you.
Fortunately, you have a tool available to you which will help you find out what is going on: the debugger. How you use it depends on your compiler system, but a quick Google for the name of your IDE and "debugger" should give you the info you need.
Put a breakpoint on the first line in the function, and run your code through the debugger. Then look at your code, and at your data and work out what should happen manually. Then single step each line checking that what you expected to happen is exactly what did. When it isn't, that's when you have a problem, and you can back-track (or run it again and look more closely) to find out why.
Sorry, but we can't do that for you - time for you to learn a new (and very, very useful) skill: debugging!