Dynamic pointing array to a dynamic 2 dimensions array? - c

Question

I need to allocate a char** array that points to a 2 dimensions chars array.
Eventually, I want to point to a "cell" like players[playerNum][Row][Col].
This is what I wrote so far, but it fails.
It is hard to understand the logic behind it, so if you can explain me whats wrong it will be great.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[]) {
int numOfPlayers;
int i,j;
char** players = (char **)malloc(sizeof(char**)*numOfPlayers); // players array
for (i=0 ; i<numOfPlayers ; i++){
players[i] = (char *)malloc(sizeof(char*)*10); // each player 1st D array
}
for (i=0 ; i<10 ; i++){
for (j=0 ; j<10 ; j++){
players[i][j] = (char *)malloc(sizeof(char*)*10);
}
}
return 0;
}

Answer 1

Allocation in your code is wrong!
Do like this:
char** players = malloc(sizeof(char*) * numOfPlayers);
^ remove one *
for (i=0 ; i<numOfPlayers ; i++){
players[i] = malloc(sizeof(char)* 10); // each player 1st D array
// ^ remove * it should be char
}
note: sizeof(char) != sizeof(char*).
You don't need second nested for loop too. (just above code is fine)
Also avoid casting return value from malloc/calloc in C
Note A mistake in your code is that numOfPlayers is not initialized (you are trying with garbage value).
Comment:
But then, i only have 2D array. i need an array that each cell of him points to a 2D array like so... you misunderstood my question
Read if you wants - a matrix of String or/ 3D char array
To allocate a matrix like: players[playerNum][Row][Col]
char ***players;
players = calloc(playerNum, sizeof(char**));
for(z = 0; z < playerNum; z++) {
players[z] = calloc(Row, sizeof(char*));
for(r = 0; r < Row; r++) {
players[z][r] = calloc(Col, sizeof(char));
}
}
Edit If you wants to allocate continues memory for data, then you can use following technique. It will also be preferable because it makes less call of malloc function.
char *players_data, // pointer to char
***players; // pointer to 2D char array
players_data = calloc(playerNum * Row * Col, sizeof(char)); //1 memory for elements
players = calloc(playerNum, sizeof(char **)); //2 memory for addresses of 2D matrices
for(i = 0; i < playerNum; i++){
players[i] = calloc(Row, sizeof(char*)); //3 memory for data cols
for(r = 0; r < Row; r++){ //4 Distributed memory among rows
players[i][r] = players_data + (i * Row * Col) + (r * Col);
}
}
A good reference to learn: Dynamic Three Dimensional Arrays in C\C++