Reading and processing from text file to 2D integer array, with statements in between - c

Question

I'm making a maze solver using Breadth-first search. Consider the following list of numbers in a text file
10 20
1 1
10 20
5 1
4 2
3 3
1 10
2 9
3 8
4 7
5 6
6 5
7 4
8 3
Where the first row denotes a size of my maze (10x20), the second row denotes the starting position coordinates (1x1),and the third row denotes the ending position(10x20). Every row after the third row represents the coordinate where a block in the maze will be (aka will have to move around it).
Here's what this particular board will look like:
**********************
*s........*..........*
*........*...........*
*..*....*............*
*.*....*.............*
**....*..............*
*....*...............*
*...*................*
*..*.................*
*....................*
*...................e*
**********************
What I am trying to do:
If my text file has impossible coordinates for either the size or start/end coordinates, ignore those coordinates and continue processing input.
example:
10 0 => Invalid: Maze sizes must be greater than 0
15 7 => Maze becomes size 15 x 7
10 20 => Invalid: column 20 is outside range from 1 to 7
5 1 => Starting position is at position 5, 1
24 2 => Invalid: row 24 is outside of range from 1 to 15
3 3 => Ending position is at position 3, 3
1 10 => Invalid: column 10 is outside range from 1 to 7
2 9 => Invalid: column 9 is outside range from 1 to 7
3 8 => Invalid: column 8 is outside range from 1 to 7
4 7
5 6
5 1 => Invalid: attempting to block starting position
6 5
7 4
8 3
I know I'm supposed to use some fprintf or fscanf loop until the end of file is reached.
Can someone start me off in the right direction?
I want to print all coordinates in the file, with error messages further in the line, if necessary.

Answer 1

Is the problem you are trying to ask how to read all the points? If so you can do something like the following:
int n1, n2;
FILE * fp = fopen("myfile.txt", "r");
//...read first three lines and do what you need with them
//read rest of points
while( fscanf(fp, "%d %d", &n1, &n2) ) {
if (checkPoints(n1,n2)) // check points are valid
addPointsToBoard(n1,n2); // add to board
}
If you're asking how to implement something like checkPoints I'd say you haven't given enough information of how you plan to implement your code for someone to help
NOTE: This assumes you have a well formed input file. If you are concerned about invalid inputs you will need to do sanity checking
EDIT Based upon comment here is a way you can do a sanity check on the matrix size input (first line)
int valid_size = 0;
while(1) {
if ( fsanf(fp, "%d %d", &n1, &n2) )
valid_size = checkMatrixSizes(n1,n2);
else
exit(1); //never finding valid matrix size in file
if (valid_size)
break
}
The above loop will continuously loop until checkMatrixSizes finds valid sizes (I would also suspect it would create your board, etc. The above is pseudo code and far from complete). You could do similar loops for the second and third inputs. It should be noted that this code simply ignores any invalid input and moves on, which I think is the behavior you want based upon your question. Other behaviors might include adjusting the input to the closest acceptable value (i.e. if a column is out of range, set column to the highest possible value).