I don't know how to fix this code for it to print a sudoku puzzle with it corresponding solution.

public class Sudoku

$\{$

int$[]$ mat$[]$;

int N; $//$ number of columns$/$rows$.$

int SRN; $//$ square root of N

int K; $//$ No$.$ Of missing digits

$//$ Constructor

Sudoku$($int N$,$ int K$)$

$\{$

this.N $=$ N;

this.K $=$ K;

$//$ Compute square root of N

Double SRNd $=$ Math.sqrt$($N$)$;

SRN $=$ SRNd$.$intValue$()$;

mat $=$ new int$[$N$][$N$]$;

$\}$

$//$ Sudoku Generator

public void fillValues$()$

$\{$

$//$ Fill the diagonal of SRN x SRN matrices

fillDiagonal$()$;

$//$ Fill remaining blocks

fillRemaining$(0,$ SRN$)$;

$//$ Remove Randomly K digits to make game

removeKDigits$()$;

$\}$

$//$ Fill the diagonal SRN number of SRN x SRN matrices

void fillDiagonal$()$

$\{$

for $($int i $=0$; ii$==$j

fillBox$($i$,$ i$)$;

$\}$

$//$ Returns false if given $3$ x $3$ block contains num.

boolean unUsedInBox$($int rowStart, int colStart, int num$)$

$\{$

for $($int i $=0$; i$=$N && i$=$N && j$>=$N$)$

return true;

if $($i $<$ SRN$)$

$\{$

if $($j $<$ SRN$)$

j $=$ SRN;

$\}$

else if $($i $<$ N$-$SRN$)$

$\{$

if $($j$==($int$)($i$/$SRN$)*$SRN$)$

j $=$ j $+$ SRN;

$\}$

else

$\{$

if $($j $==$ N$-$SRN$)$

$\{$

i $=$ i $+1$;

j $=0$;

if $($i$>=$N$)$

return true;

$\}$

$\}$

for $($int num $=1$; num$<=$N; num$++)$

$\{$

if $($CheckIfSafe$($i$,$ j$,$ num$))$

$\{$

mat$[$i$][$j$]=$ num;

if $($fillRemaining$($i$,$ j$+1))$

return true;

mat$[$i$][$j$]=0$;

$\}$

$\}$

return false;

$\}$

$//$ Remove the K no$.$ of digits to

$//$ complete game

public void removeKDigits$()$

$\{$

int count $=$ K;

while $($count $!=0)$

$\{$

int cellId $=$ randomGenerator$($N$*$N$)-1$;

$//$ System.out.println$($cellId$)$;

$//$ extract coordinates i and j

int i $=($cellId$/$N$)$;

int j $=$ cellId$\%$N;

$//$ System.out.println$($i$+""+$j$)$;

if $($mat$[$i$][$j$]!=0)$

$\{$

count$--$;

mat$[$i$][$j$]=0$;

$\}$

$\}$

$\}$