CareerCup

For starters Im sure you know that the adjacency matrix is one of the worst ways to represent a graph because of its large memory requirements (n^2).

To determine if a vertex is adjacent to another we need to scan the matrix in the row i and column y, if the value at Matrix[i][j] == 1 then those vertex are adjacent. a common variation to this problem might be in a weighted graph, were, instead of 1 and 0s you have actual numbers representing the cost. that does not seem to be the case here

So the first thing you need to do is to represent the adjacency matrix in memory thats a 2D array.

To dinamycally allocate a 2D array in the following code might do the trick, (please keep in mind Im a CPP programer so the syntax might be a bit off)

int matrixSize = getVertexCount();//assumed to return an int with number of vertices

int** Matrix = new int*[matrixSize];
for (int i=0; i<matrixSize; i++){
  Matrix[i] = new int[matrixSize];
}

Now you have the array, its time to fill it up, please not that new should be replaced with malloc() in the above code to comply with the C ONLY requirement.

Im assuming that your file contains the actual number of vertices and that you have that number stored in a variable already... in case you dont, all you gotta do to get is scan the first line of the file counting the numbers of 'comas' and adding one to it

//always a good idea to get strings by reference, this method reads a line of text
//and fill its corresponding row
void fillMatrixRow(int rowNum, const string &data){
	vector<string> numbers = splitString(data, ',');//assuming we have this somewere
        for(int i=0; i< numbers.size(); i++){
           int n = atoi(numbers[i],10);
           Matrix[rowNumber][i] = n;
        }
}

void fillMatrixFromDisk(const char* fileName){
	fstream f(fileName);
	if ( !f.is_open() ) return;
	int currentRow =0;
	while (!f.eof){
	  std::getline(f, currentLine);
          fillMatrixRow(currentRow, currentLine);
	}
}

Ok so now you have a 2D array filled from the info on th HDD all that is left is to read i and j from the console and ouput the result

int main(){
	int i,j;
	cout << "Value of i:";
        cin >>i;
	cout << "Value of J:";
        cin >>j;

	if (Matrix[i][j] == 1 )
		cout << "Vertex are adjacent";
        else
		cout << "Vertex are NOT adjacent";

return 1;
}

Thats pretty much it, most of the code is C++ all you gotta do is replace cout, with pritnf, and cin with scanf, also the string tokenization used an STL vector that you might need to replace with a buch of calls to strtok().

I hope you get the gist, an apologies for the code it was written straight into the comment box without double checking if the syntax was ok