Problem with Printing the Element of 2D Char Array(C)

I fill a 2D array with string. How can I check if the next string will take up place is empty or not? I am confused as I placed the strings at random start index and direction.

I want to to fill this array with str_2 (it is char pointer it include just 1 special word adress). I also want the positions of the words not to overlap

I want to fill it with random direction and random starting point like.for example words are how, good, she, it, he. briefly my code:

        char *word(char *file, char *str);

    int main() {
        char *str;
        char *str_2;
        int i,j,x,y;
        char *puzzle[20][20];
        int z;/* direction :1 left to right 2 reverse,3 top to bottom 4 reverse,5 left top cross to right bottom cross b 6 reverse,7 right top cross to left bottom cross 8 reverse;*/
        str = (char *)malloc(20);
        str_2=word("words.txt",str);//function returns pointer;             
        free(str);
    srand(time(NULL));
    x=rand()%20;
    y=rand()%20;
    z=1;//it will be rand()%8+1
  // 10 word will be filled and printed to matrix after program coding finished
     if(z==1){//left to right
     for(i=y;  ;  ){
        for(j=x;i<x+strlen(str_2);i++){//
            puzzle[i][j]=str_2;
            if(x+strlen(str_2)>20)//if it owerflow the column of the matrix)
                    puzzle[i][j]=str_2;//take word from function again

            else continue;
         }
     }
     for(i=y;  ;   ){
        for(i=x;i<x+strlen(str_2);i++   ){
        printf("%s",puzzle[i][j]);
        }
     }
     }
}

This program prints nothing i dont know what is this problem?

how**
doog*
t****
i*she
**eh*

(* is not important it should be anything when my code finish it prints something like that just different size)