bool row[9][10],col[9][10],rco[3][3][10];
int blank[81][2],cnt = 0;
bool dfs(int lev,char ** sudo,const int rsz,const int csz)
{
    if(lev >= cnt)
        return true;
    int x  = blank[lev][0],y = blank[lev][1];
    for(int i= 1; i < 10; i++)
        if(!row[x][i] && !col[y][i] && !rco[x/3][y/3][i])
        {
            sudo[x][y] = '0' + i;
            row[x][i] = col[y][i]  = rco[x/3][y/3][i] = true;
            if(dfs(lev+1,sudo,rsz,csz))
                return true;
            row[x][i] = col[y][i]  = rco[x/3][y/3][i] = false;
        }
    return false;
}

void solveSudoku(char** board, int rsz, int csz)
{
    cnt = 0;
    memset(row,0,sizeof(row));
    memset(col,0,sizeof(col));
    memset(rco,0,sizeof(rco));
    for(int r = 0; r < rsz; r++)
        for(int c = 0,tmp; c < csz; c++)
            if(isdigit(tmp=board[r][c]))
                row[r][tmp-'0'] = col[c][tmp - '0'] = rco[r/3][c/3][tmp -'0'] =  true;
            else
            {
                blank[cnt][0] = r;
                blank[cnt++][1] = c;
            }
    dfs(0,board,rsz,csz);
}