How to Initialize a Multidimensional Char Array in C?

Question

I'm trying to convert some code from C# to C so that it can be burnt onto a microcontroller.

Could someone please tell me how I would convert a two dimensional string array in C# into something in C?

My C# code looks like this:

string[,] DirectionPosition = {{"00", "10", "", "01", ""},
                                        {"01", "11", "", "02", "00"},
                                        {"02", "12", "", "03", "01"},
                                        {"03", "13", "", "04", "02"},
                                        {"04", "14", "", "", "03"},
                                        {"10", "20", "00", "11", ""},
                                        {"11", "21", "01", "12", "10"},
                                        {"12", "22", "02", "13", "11"},
                                        .
                                        .
                                        .
                                        .
                                        {"44", "", "34", "", "43"},};

And moreover, how would I access the elements? In C# if I wanted the second element in the third row it would simply be DirectionPosition[2,1] but what is the equivalent of that when there is no string in C much less 2-D string arrays?

Answer 1

char DirectionPosition[][ 5 ][ 3 ] = {{"00", "10", "", "01", ""},
                                    {"01", "11", "", "02", "00"},
                                    {"02", "12", "", "03", "01"},
                                    {"03", "13", "", "04", "02"},
                                    {"04", "14", "", "", "03"},
                                    {"10", "20", "00", "11", ""},
                                    {"11", "21", "01", "12", "10"},
                                    {"12", "22", "02", "13", "11"},
                                    .
                                    .
                                    .
                                    .
                                    {"44", "", "34", "", "43"},};

C has no inbuilt string class, you have to make do with character arrays. You could alternatively use pointers to pointer to char.

Answer 2

The easiest way to do it is with char pointers as follows:

char *DirectionPosition[9][5] = {
    {"00", "10", "",   "01", ""  },
    {"01", "11", "",   "02", "00"},
    {"02", "12", "",   "03", "01"},
    {"03", "13", "",   "04", "02"},
    {"04", "14", "",   "",   "03"},
    {"10", "20", "00", "11", ""  },
    {"11", "21", "01", "12", "10"},
    {"12", "22", "02", "13", "11"},
    {"44", "",   "34", "",   "43"}
};

The element "10" in the first line is referenced as DirectionPosition[0][1] (zero-based, first index is line, second is column).

Answer 3

I recommend deciding the maximum length of strings and maximum number of strings per row and telling the compiler, e.g.:

typedef char string[3];
typedef string s5[5];

    s5 DirectionPosition[] = {{"00", "10", "", "01", ""}, {"01", "11", "", "02", "00"}, {"02", "12", "", "03", "01"}, {"03", "13", "", "04", "02"}, {"04", "14", "", "", "03"}, {"10", "20", "00", "11", ""}, {"11", "21", "01", "12", "10"}, {"12", "22", "02", "13", "11"}, {"44", "", "34", "", "43"},};

Now, DirectionPosition[2][1] &c will let you access specific strings in the matrix.

Answer 4

There's a slightly simpler way of doing this without all the extra brackets:

#include <stdio.h>

int main(int argc, char **argv) {

char DirectionPosition[][ 5 ][ 3 ] = {"00", "10", "", "01", "",
                                    "01", "11", "", "02", "00",
                                    "02", "12", "", "03", "01",
                                    "03", "13", "", "04", "02",
                                    "04", "14", "", "", "03",
                                    "10", "20", "00", "11", "",
                                    "11", "21", "01", "12", "10",
                                    "12", "22", "02", "13", "11",
                                    "44", "", "34", "", "43"};

    printf("dp[1][1] == %s\n", DirectionPosition[1][1]);
    printf("dp[1][2] == %s\n", DirectionPosition[1][2]);
    printf("dp[1][3] == %s\n", DirectionPosition[1][3]);

    return;
}