In C, how can I incrementally load the values from a one dimensional array into a two dimensional array?

I'm trying to build a Rail Fence Encryptor, so I need to load a one dimensional array, which goes across, in to a two dimensional array, from top to bottom, so it the positions look like this





***1D array***





1 2 3 4 5 6 7 8 9





***2D array***





1 4 7


2 5 8


3 6 9





The code then needs to be encrypted by reading the resultant rows, thus;





147 258 369





I'm programming in the C language





More information about the Rail Fence Cipher can be found at





http://en.wikipedia.org/wiki/Rail_fence





I also need to make a decrypter, but I don't know where to start with that!





If you could help me with any part of that, I will be VERY grateful!





Thanks!

In C, how can I incrementally load the values from a one dimensional array into a two dimensional array?
The following should provide the two dimensional array lookup:





int encryptDim1[] = {1,2,3,4,5,6,7,8,9};


int encryptDim2[3][3], row, col;


for (row=0; row%26lt;3; row++)


for (col=0; col%26lt;3; col++)


encryptDim2[row][col] = encryptDim1[row*3+col];





As for a decrypter, it appears Rail Fence decoding takes more code/effort than encoding. Below is some encode/decode source code I found at the link below:





function rail_decode(t, r)


{


var o_idx = new Array((r - 1) * 2);


var out_a = new Array(r);


var i, j, k, o=0;





for (i = 0; i %26lt; o_idx.length; i ++)


{


j = (o + i) % o_idx.length;


if (j %26lt; r)


{


o_idx[i] = j;


}


else


{


o_idx[i] = (2 * (r - 1)) - j;


}


}





for (i = 0; i %26lt; out_a.length; i ++)


{


out_a[i] = 0;


}





for (i = 0; i %26lt; t.length; i ++)


{


out_a[o_idx[i % o_idx.length]] ++;


}





j = 0;


for (i = 0; i %26lt; out_a.length; i ++)


{


out_a[i] = t.slice(j, j + out_a[i]);


j += out_a[i].length;


}





j = "";


for (i = 0; i %26lt; t.length; i ++)


{


k = o_idx[i % o_idx.length];


j += out_a[k].charAt(0);


out_a[k] = out_a[k].slice(1, out_a[k].length);


}





return j;


}





function rail_encode(t, r)


{


var o_idx = new Array(r * 2 - 2);


var out_a = new Array(r);


var i, j, o=0;





for (i = 0; i %26lt; r; i ++)


{


o_idx[i] = i;


out_a[i] = ""


}


for (j = 0; j %26lt; r - 2; j ++)


{


o_idx[i + j] = i - (j + 2);


}





for (i = 0; i %26lt; t.length; i ++)


{


out_a[o_idx[o]] += t.charAt(i);


o = (o + 1) % o_idx.length


}





j = "";


for (i = 0; i %26lt; r; i ++)


{


j += out_a[i];


}





return j;


}
Reply:The answer to this is a nested for loop





for ()


{





for ()





{





}





}





That's basically all I can tell you without giving too much
Reply:It's been a while since I've done C, but I think it's similar to Java. You declare a 2D array something like this...





int[][] twoDeeArray;





This is an array of arrays. You access the positions like this...





twoDeeArray[0][0] = 1; //First position in the first array


twoDeeArray[0][1] = 2; //Second position in the first array, etc.


twoDeeArray[1][0] = X; //First position in the second array.





Gluck.
Reply:Find a way to walk through one of your arrays, and map it's form onto the other. For example, walk along the width of the 2D, going down each column one at a time, and use a variable to index your 1D array.





This means that your outer loop (the row loop) has a variable that will go from 0 to the width of your 2D array - 1, and an inside loop (the column loop) goes from 0 to the hight of your 2D - 1.





Then you could use something like this "twoD[row][column] = OneD[i++]" to put a value from the 1D into the 2D.





To decrypt, you just reverse that one part: "OneD[i++] = twoD[row][column]", and now you're taking things off in order.





Make sure that your 1D will fit into the 2D for encryption and visa-versa for decryption.