Comparing characters in two arrays of strings

[evapisces]

Hello. I'm having some trouble with a section of a project I'm working on. The general task of the program is to read in a list of student exam answers from a file along with an answer key, score the answers, and print some reports on the results.

Okay, so I have created the following arrays:

char ansKey[MAXLEN];
char id[MAXCT][5];
char responses[MAXCT][MAXLEN];
int indices[MAXCT];

MAXCT = 40 and MAXLEN = 25

I'm am working on the first report. I have to grade the answers against the answer key. So I'm pretty sure I have to do a string compare where I compare each element of the answer key to the repective element in each student's responses. However, I'm not sure how to do this. Here's the function where I fill the arrays and compare the answer key and student responses:


int fillArrays(char key[], char iden[][5], char answers[][MAXLEN], int index[], int ct)
{
ifstream inFile;
inFile.open("P7Grades.txt");

if (!inFile)
{
cout << "Cannot find input file.\n\n";
system("PAUSE");
exit(1);
}

inFile >> key;
int i = -1;

while (!inFile.eof() )
{
i++;
inFile >> iden[i] >> answers[i];
index[i] = i;
}

for (int j = 0; i < ct; j++)
{
for (int k = 0; k < 20; k++)
{
if (strcmp(key[k], answers[j][k]) != 0)
cout << "*" << answers[j][k] << " ";
}
}

return i;
inFile.close();
}



When I run the code, I get this error message:


invalid conversion from 'char' to 'const char*'
(initializing argument 1 of 'int strcmp(const char*, const char*))
and
invalid conversion from 'char' to 'const char*'
(initializing argument 2 of 'int strcmp(const char*, const char*))



I'm not sure what I'm doing wrong. Any help is greatly appreciated. If you need additional info, please let me know.

I'm fairly new to C++, so if you guys could explain things as simple as possible, I would really appreciate it.
Thanks in advance :)

[stephendoyle75]

The clue is in the error message. Strcmp compares 2 strings (or more specifically, char* strings). You are passing a single character as both parameters and this is giving you the compiler error.

What format are the keys in? Can you give an example?

[evapisces]

Sure. Here's the key and the first few student responses from the file:


bcddacbaaebdbecceacb
H926 bcedaccbaexdbedceabb
H080 acddacbaxebdbecaeacb
H233 bcddacbaaebdbecceacb

The first line is the answer key and the other lines are the student's ID number followed by their responses.

[stephendoyle75]

Ok, so you really do want to compare the answer against the key one character at a time. You don't need strcmp() for this, instead use a simple equality comparison, e.g.:

for (int k = 0; k < 20; k++)
{
if (key[k] !=answers[j][k])
cout << "*" << answers[j][k] << " ";
}