bool cuadrante(char v,ulong n,ulong m,ulong n2,ulong m2, char [][] grid){
    ulong i,j;
    ulong lim,lim2;
    lim = 3 * (n+1);
    lim2 = 3 * (m+1);
    bool bandera = true;
    for (i=3*n;i<lim;i++){
        for(j=3*m;j<lim2;j++){
            if(i != n2 || j!=m2){
                if(v == grid[i][j] ){
                    bandera = false;
                }
            }
        }
    }
    return bandera;
}
bool findCoincidences(char[][] grid,ulong n ,ulong  m){
    char valor = grid[n][m];
    ulong i,j,k;
    for (i = 0; i<= 8; i++){
        if(!(i==m)){
            if(grid[n][i]==valor){
                return false;
            }
        }
    }
    for (i = 0; i<= 8; i++){
        if(!(i==n)){
            if(grid[i][m]==valor){
                return false;
            }
        }
    }
    // buscar en cuadrante
    j = n/3;
    k = m/3;
    bool buscar = cuadrante(valor,j,k,n,m,grid);
    if(!buscar){
        return false;
    }
    return true;
}
bool sudoku2(char[][] grid) {
    foreach(i,e; grid){
        foreach(j,v;e){
            if(!(v == '.')){
                bool valido = findCoincidences(grid,i,j);
                if (!valido){
                    return false;
                }
            }
        }
    }
    return true;
}