Qfyilyi

My uni tasked me with writing a program that reads the input and stores it into a dynamic 2D array, but we haven't covered that topic. I'm encountering a problem with my implementation, as it is skipping the first character in each line. I know the code is not top quality, but I just can't figure out why it skips the first char.

#include <stdio.h>

#include <stdlib.h>

#include <assert.h>





#define MULT 3

#define DIV 2



char *read_line(int *col_size, int *max_c) {

    char *line = NULL;

    int size = *col_size;

    int i, c;

    line = malloc(size * sizeof *line);

    for (i = 0; ((c = getchar()) != 'n') && (c != EOF); ++i) {

        if (i == size) {

            size = 1 + size * MULT / DIV;

            line = realloc(line, size * sizeof *line);

            assert(line != NULL);

        }

        line[i] = c;

    }

    if (i > *max_c)

        *max_c = i;

    if (size > *col_size)

        *col_size = size;

    return line;

}



char **read(int *row, int *col) {

    char **input = NULL;

    int row_size = 0;

    int col_size = 0;

    int i, c;

    int max_c = 0;



    for (i = 0; (c = getchar()) != EOF; ++i) {

        if (i == row_size) {

            row_size = 1 + row_size * MULT / DIV;

            input = realloc(input, row_size * sizeof *input);

            assert(input != NULL);

        }

        input[i] = read_line(&col_size, &max_c);

    }

    *row = i;

    *col = max_c;

    return input;

}





int main(void) {

    int row_size, col_size, i, j;

    char **board = read(&row_size, &col_size);

    for (i = 0; i < row_size; ++i) {

        for (j = 0; j < col_size; ++j)

            putchar(board[i][j]);

        putchar('n');

    }

    free(board);

    return 0;

}

for (i = 0; (c = getchar()) != EOF; ++i) {

in read() eats up the first character of a line before read_line() gets to see it. You'll have to find some other way to check for EOF. For example with

for (i = 0; !feof(stdin); ++i) {

Also, you don't zero-terminate your strings. Change your reading loop to

char *read_line(int *col_size, int *max_c) {

    int size = *col_size ? *col_size : 1;  // at least 1 for the terminating 0

    char *line = malloc(size * sizeof *line);



    if(!line)

        return NULL;



    int i, c;

    for (i = 0; ((c = getchar()) != 'n') && (c != EOF); ++i) {

        if(i == size) {

            size = 2 + size * MULT / DIV;  // note the 2

            // ...

        }

        // ...

    }

    line[i] = '';

to do so.

for (i = 0; i < row_size; ++i) {

  for (j = 0; j < col_size; ++j)

      putchar(board[i][j]);  // accesses memory that isn't yours

  putchar('n');             // if not all rows are of the same length.

}

To avoid reading memory out-of-bounds, change that to

for (i = 0; i < row_size; ++i) {

    for (j = 0; board[i][j] != ''; ++j)

        putchar(board[i][j]);

    putchar('n');

}

since you now have zero-terminated strings. Or why not just use puts()?

for (i = 0; i < row_size; ++i)

    puts(board[i]);

free(board);

That won't deallocate the memory you allocated for the rows. You'd have to

for (i = 0; i < row_size; ++i)

    free(bard[i]);

free(board);