bool estValide (int tab[9][9],int position){
    int i,j,nb;

    if(position==81){
        return true;
    }
    i=position/9;
    j=position%9;
    if(tab[i][j]!=0){
        return estValide(tab, position+1);
    }
    else{
            for(nb=1;nb<=9;nb++){
                if(absentSurLigne(nb,tab,i) && absentSurColonne(nb,tab,j) && absentSurBloc(nb,tab,i,j)){
                    tab[i][j]=nb;

                    if(estValide(tab,position+1)){
                    return true;
                    }
                }
            }
        }
    tab[i][j]=0;
    return false;
}