Htykuut

hello guys this is my code :

#include <stdio.h>

#include <stdlib.h>



int power(int a, int b) {

    int exponent = b, result = 1;

    while (exponent != 0) {

        result = result * a;

        exponent--;

    }

    //printf("%d",result);

    return result;

}



int fill_it(char ** p, int N, int fliptimes, int column2) {

    if (N < 0) return 0;

    int counter = 0, l;

    char a = 'H';

    for (l = 0; l < power(2, fliptimes); l++) {

        p[l][column2] = a;

        counter++;

        if (counter == (power(2, N) / 2)) {

            counter = 0;

            if (a == 'H') a = 'T';

            if (a == 'T') a = 'H';

        }

    }

    fill_it(p, N--, fliptimes, column2++);

}



int main() {

    int i, fores, j, l, m;

    char ** p;

    printf("how many times did you toss the coin?:");

    scanf("%d", & fores);

    p = (char ** ) malloc((power(2, fores)) * sizeof(char * ));

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

        p[i] = (char * ) malloc(fores * sizeof(char));

    fill_it(p, fores, fores, 0);

    for (l = 0; l < power(2, fores); l++) {

        for (m = 0; m < fores; m++) {

            printf("%c", p[l][m]);

        }

    }

    printf(",");

}

it does compile.But when i run the program it returns a "segmantation fault (core dumped)" error

i know it means that i tried to access memory,i dont have acces to but i dont understand which part of the program is defective

The problem is, you're not allocating enough memory. This line is fine

p = (char ** ) malloc((power(2, fores)) * sizeof(char * ));

but this loop is only allocating memory for part of the 2-dimensional array.

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

    p[i] = (char * ) malloc(fores * sizeof(char));

The memory allocation should look more like this...

foresSquared = power(2, fores);

p = malloc(foresSquared*sizeof(char *));

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

    p[i] = malloc(fores);

Since the result of power is going to be consistent, it makes sense to store the value in a variable and use that rather than recalculating it. It'll make the code clearer too.

You also don't need to cast the return value of malloc as C handles that for you. And sizeof(char) isn't needed as it's guaranteed to always be 1.