Latin Square algorithm problem

[Sejoro]

Hey again,

I'm trying to write a program that will output a random valid Latin Square (9x9 square of numbers 1 - 9 with no repetition in the rows and columns) and can't get my numbers to not repeat. I figured that the code I have now would be enough, but it doesn't seem to be working. Could somebody help me out?

#include <iostream>
#include <ctime>
using namespace std;

int main(){

srand(time(0));
int grid[9][9];
int test = 0;
int check = 0;
for(int i = 0; i < 9; i++){

for(int j = 0; j < 9; j++){

grid[i][j] = rand() % 9 + 1;

}

}

for(int loop = 0; loop < 9; loop++){

for(int run = 0; run < 9; run++){

test = grid[run][run];

for(int repeat = 0; repeat < 9; repeat++){

check = grid[repeat][repeat];
if(test == check){

grid[repeat][repeat] = rand() % 9 + 1;
repeat = -1;

}

}

}

}
//Printing the Latin Square
int rows = 1;
for(int print = 0; print < 9; print++){

for(int dim = 0; dim < 9; dim++){

cout << grid[print][dim] << " ";
if(rows < 9){
rows++;
}
else{
cout << endl;
rows = 1;
}
}

}

system("PAUSE");
return 0;

}

[whodgson]

Hey again,

I'm trying to write a program that will output a random valid Latin Square (9x9 square of numbers 1 - 9 with no repetition in the rows and columns) and can't get my numbers to not repeat. I figured that the code I have now would be enough, but it doesn't seem to be working. Could somebody help me out?

#include <iostream>
#include <ctime>
using namespace std;

int main(){

srand(time(0));
int grid[9][9];
int test = 0;
int check = 0;
for(int i = 0; i < 9; i++){

for(int j = 0; j < 9; j++){

grid[i][j] = rand() % 9 + 1;

}

}

for(int loop = 0; loop < 9; loop++){

for(int run = 0; run < 9; run++){

test = grid[run][run];

for(int repeat = 0; repeat < 9; repeat++){

check = grid[repeat][repeat];
if(test == check){

grid[repeat][repeat] = rand() % 9 + 1;
repeat = -1;

}

}

}

}
//Printing the Latin Square
int rows = 1;
for(int print = 0; print < 9; print++){

for(int dim = 0; dim < 9; dim++){

cout << grid[print][dim] << " ";
if(rows < 9){
rows++;
}
else{
cout << endl;
rows = 1;
}
}

}

system("PAUSE");
return 0;

}

.......i think yiu need to launch rand from seed.

[Laharl]

He called srand(), no issues there. My usual solution to this sort of thing is to use a while loop: while(randomly chosen value is already there): choose another random value. It's not particularly quick, but it usually works OK.

[JosAH]

I wrote the following little monster once (pre-ANSI/C) and it even doesn't need
an NxN square matrix to produce a magic square of size N (N must be odd and
supplied on the command line). Have fun.

main(o,O0)char**O0;{int OO,O;O=--o?atoi(O0[!0]):!
0;for(o=((OO=O*O)-O+!0+!0)>>!0;OO;o+=((--OO%O)?-!
0:((((o-!0)%O)?O:0)+!0))-(((o-!0)%O)?O:0)){printf
("\n%*d "+!!(OO%O),!0<<!0<<!0,o+=(o<!0)?O*O:0);}}
 

kind regards,

Jos