Is there a more concise method?

I would appreciate it if someone could look over this code and tell me if there is a more precise method of going through and comparing individual characters of a string. The code below is a function called upon by the main function to compare individual characters of 2 strings.

Code:

int CheckAnswer(string)
{
	int count;
	
	if(key == answer)
	{
		score = 20;
	}
	else if (key.length() == answer.length())
	{
		count = 0;
		score = 0;
		while (count <= 20 && score <= 20)
		{
			if (key.substr(0,1) == answer.substr(0,1))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(1,2) == answer.substr(1,2))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(2,3) == answer.substr(2,3))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(3,4) == answer.substr(3,4))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(4,5) == answer.substr(4,5))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(5,6) == answer.substr(5,6))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(6,7) == answer.substr(6,7))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(7,8) == answer.substr(7,8))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(8,9) == answer.substr(8,9))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(9,10) == answer.substr(9,10))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(10,11) == answer.substr(10,11))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(11,12) == answer.substr(11,12))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(12,13) == answer.substr(12,13))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(13,14) == answer.substr(13,14))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(14,15) == answer.substr(14,15))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(15,16) == answer.substr(15,16))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(16,17) == answer.substr(16,17))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(17,18) == answer.substr(17,18))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(18,19) == answer.substr(18,19))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
			if (key.substr(19,20) == answer.substr(19,20))
			{
				score++;
				count++;
			}
			else
			{
				count++;
			}
		}

	}
	else if (key > answer)
	{
		score = -1;
	}
	else if (key < answer)
	{
		score = -2;
	}
	else if (something)
	{
		score = -3
	}
return 0;

}

Thanks-

something like this maybe?

Code:

for(int X = 0;X<20;X++)
{
       if (key.substr(X,X+1) == answer.substr(X,X+1))
	{
		score++;
	}
}

Are the lengths of the two strings always 20? If so, then that for loop will be OK.

Otherwise I might use:

Code:

for(int X = 0; x != key.length(); ++X)

Your larger problem is in your calls to substr(). substr(i,n) gets the substring starting at position i, n characters long. If your key was "abcdefgh" then substr(i,n) is below:

Code:

i    n     substr(i,n)
-----------------------
1   1     "a"
2   3     "bcd"
3   4     "cdef"
4   5     "defgh"
5   6      error!

That last one should give you an error since there is no string starting at position 5, 6 characters long. Try this instead:

Code:

for(int i = 0; i != key.length(); ++i)
{
      if (key.substr(i,1) == answer.substr(i,1))
            ++score;
}

That way you're just comparing one character at a time. Come to think of it, you don't even need substr to compare one character at a time, I'm pretty sure you can just do this:

Code:

for(int i = 0; i != key.length(); ++i)
{
      if (key[i] == answer[i])
          ++score;
}

I'm pretty sure that will work, but I don't have a compiler on this machine, so I left the substr version in the post, just in case - you'll have to test it.

Hey, I just wanted to say thanks for your help guys. Your timly reply was much appreciated and your advice worked with a little tweaking of my program... and now i have a better understanding of the way that substr() function works.
-Thanks