i have a problem with initializing a 2D array in C using user input-CodePudding

i have this code:

#include <stdio.h>
void set_board_size() {
    int Xsize, Ysize, check = 1;
    while (check == 1) {
        printf("enter X and Y sizes(in that order): ");
        scanf_s("%d", &Xsize);
        scanf_s("%d", &Ysize);
        if ((Ysize >= 4 && Ysize <= 9) || (Xsize >= 4 && Xsize <= 9)) {
            break;
        }
        else
            printf("---------");
    }
    int mat[Xsize][Ysize];
}
void main() {
    set_board_size();
}

on line

int mat[Xsize][Ysize];

it says i must use a constant value but how can i do that with user input?

CodePudding user response：

You can use this:

int** mat = (int**)malloc(Xsize * sizeof(int*));
for (size_t i = 0; i < Xsize; i  )
{
    mat[i] = (int*)malloc(Ysize * sizeof(int));
}

And don't forget to deallocate everything when you're done using it:

for (size_t i = 0; i < Xsize; i  )
{
    free(mat[i]);
}
free(mat);

You will probably need to change this:

int Xsize, Ysize;

To this:

size_t Xsize, Ysize;

And this:

scanf_s("%d", &Xsize);
scanf_s("%d", &Ysize);

To this:

scanf_s("%zu", &Xsize);
scanf_s("%zu", &Ysize);