CODEWITHSUNDEEP
cstdio
roxrook
roxrook

Reputation: 13853

How to read an 2 dimensional array from file using C?

I tried:

void read_grid_from_file( int** grid, const size_t row, const size_t column, FILE* inf ) {
    size_t x, y;
    for( x = 0; x < row; ++x ) {
        for( y = 0; y < column; ++y ) {
            fscanf( inf, "%d", &grid[x][y] );
            printf( "%d ", grid[x][y] );
        }
        printf( "\n" ); 
    }
}

int main( int argc, char *argv[] ) {
    FILE* inf; // input file stream
    FILE* outf; // output file stream
    char pbm_name[20]; 
    size_t row = 0;
    size_t column = 0;
    /*
    if( argc != 3 ) {
        prn_info( argv[0] );
        exit( 1 );
    }
    */
    inf = fopen( "infile.txt" , "r" );
    outf = fopen( "outfile.txt", "w" );
    fgets( pbm_name, 20, inf ); 
    fscanf( inf, "%d", &row );
    fscanf( inf, "%d", &column );
    int** grid = allocate_memory_for_grid( row, column );
    read_grid_from_file( grid, row, column, inf );
    show_grid( grid, row, column ); //for debugging
}

The input file is:

P1
12 14
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 0 0 0 0
1 1 1 1 1 1 1 1 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 0 0 0 0 0 0 0 0 0 0
1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1

The output is:

1 1 1 1 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 0 0
0 0 0 0 0 0 0 0 1 1 0 0 0 0
0 0 0 0 0 0 1 1 0 0 0 0 0 0
0 0 0 0 1 1 0 0 0 0 0 0 0 0
0 0 1 1 1 1 1 1 1 1 0 0 0 0
1 1 1 1 1 1 1 1 0 0 0 0 1 1
0 0 0 0 0 0 0 0 0 0 1 1 0 0
0 0 0 0 0 0 0 0 1 1 0 0 0 0
0 0 0 0 0 0 1 1 0 0 0 0 0 0
0 0 0 0 1 1 1 1 1 1 1 1 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1
Press any key to continue . . .

Where did that matrix come from?

Upvotes: 2

Views: 10386

Answers (4)

khachik
khachik

Reputation: 28693

You read row and then column. Should be vice versa, column then row.

Upvotes: 1

wnoise
wnoise

Reputation: 9922

You appear to be reading a .pbm file. You may want to consider using the netpbm library, if the license is suitable for your purposes.

Upvotes: 0

roxrook
roxrook

Reputation: 13853

Sorry guys, I think I got it, the row and column from the text file were reversed!!

Upvotes: 0

Jay
Jay

Reputation: 24895

I guess you have just reversed your row and column. There are 12 columns and 14 rows in your input file, whereas in your code, you are reading rows as columns and columns as rows.

Upvotes: 4

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