Why am I getting this error message $??$

#include

#include

#include

#include

#include

#include

#include

using namespace std;

$//$ Comparator function to sort strings first by length, then lexicographically

bool compareNumbers$($const string& first, const string& second$)\{$

if $($first$.$length$()==$ second.length$())$

return first $$ second;

return first.length$()$ second.length$()$;

$\}$

$//$ Function to read the grid from the file

vector readGrid$($const string& filename$)\{$

vector grid;

ifstream file$($filename$)$;

string line;

while $($getline$($file$,$ line$))\{$

grid.push$\_$back$($line$)$;

$\}$

file.close$()$;

return grid;

$\}$

$//$ Function to fill the grid with random digits

void fillGridWithRandomDigits$($vector& grid$)\{$

srand$($time$(0))$;

for $($string& line : grid$)\{$

for $($char& ch : line$)\{$

if $($ch $==\text{'}.\text{'})\{$

ch $=\text{'}0\text{'}+$ rand$()\%10$;

$\}$

$\}$

$\}$

$\}$

$//$ Function to extract numbers from the grid

vector extractNumbers$($const vector& grid$)\{$

vector numbers;

int rows $=$ grid.size$()$;

int cols $=$ grid$[0].$size$()$;

$//$ Extract horizontal numbers

for $($int i $=0$; i $$ rows; $++$i$)\{$

string number;

for $($int j $=0$; j $$ cols; $++$j$)\{$

if $($grid$[$i$][$j$]!=\text{'}$X$\text{'})\{$

number $+=$ grid$[$i$][$j$]$;

$\}$

else $\{$

if $($number$.$length$()>1)\{$

numbers.push$\_$back$($number$)$;

$\}$

number.clear$()$;

$\}$

$\}$

if $($number$.$length$()>1)\{$

numbers.push$\_$back$($number$)$;

$\}$

$\}$

$//$ Extract vertical numbers

for $($int j $=0$; j $$ cols; $++$j$)\{$

string number;

for $($int i $=0$; i $$ rows; $++$i$)\{$

if $($grid$[$i$][$j$]!=\text{'}$X$\text{'})\{$

number $+=$ grid$[$i$][$j$]$;

$\}$

else $\{$

if $($number$.$length$()>1)\{$

numbers.push$\_$back$($number$)$;

$\}$

number.clear$()$;

$\}$

$\}$

if $($number$.$length$()>1)\{$

numbers.push$\_$back$($number$)$;

$\}$

$\}$

return numbers;

$\}$

$//$ Function to print the grid with borders

void printGridWithBorders$($const vector& grid$)\{$

int rows $=$ grid.size$()$;

int cols $=$ grid$[0].$size$()$;

$//$ Print top border

for $($int i $=0$; i $$ cols $+2$; $++$i$)\{$

cout $$ char$(178)$;

$\}$

cout $$ endl;

$//$ Print grid with left and right borders

for $($const string& line : grid$)\{$

cout $$ char$(178)$; $//$ Left border

for $($char ch : line$)\{$

if $($ch $==\text{'}$X$\text{'})\{$

cout $$ char$(178)$; $//$ Block character for solid spaces

$\}$

else $\{$

cout $$ ch; $//$ Digits

$\}$

$\}$

cout $$ char$(178)$; $//$ Right border

cout $$ endl;

$\}$

$//$ Print bottom border

for $($int i $=0$; i $$ cols $+2$; $++$i$)\{$

cout $$ char$(178)$;

$\}$

cout $$ endl;

$\}$

$//$ Main function

int main$()\{$

string filename $=$ "BlankCrossNumber.txt$"$;

vector grid $=$ readGrid$($filename$)$;

$//$ Display initial puzzle grid

cout $$ "Today's Puzzle:" $$ endl;

printGridWithBorders$($grid$)$;

cout $$ endl;

fillGridWithRandomDigits$($grid$)$;

vector numbers $=$ extractNumbers$($grid$)$;

sort$($numbers$.$begin$(),$ numbers.end$(),$ compareNumbers$)$;

$//$ Display the list of numbers

cout $$ "Numbers to place in the puzzle:" $$ endl;

int prevLength $=-1$;

$//$ Iterate through each number

for $($const string& num : numbers$)\{$

$//$ If the current number's length differs from the previous one,

$//$ and it's not the first number, add a blank line

if $($num$.$length$()!=$ prevLength && prevLength $!=-1)\{$

cout $$ endl; $//$ Blank line

$\}$

$//$ Print the current number

cout $$ num $$ endl;

$//$ Update the previous number's length

prevLength $=$ num.length$()$;

$\}$

cout $$ endl;

$//$ Display the solution

cout $$ "Solution:" $$ endl;

printGridWithBorders$($grid$)$;

return $0$;

$\}$