I$\text{'}$m having a hard time getting this to open and read a user inputted file name. If I hard code the filename into the code it can read it no problem, so I can't tell if it's my code or if it just can't reach my file. It also won't just print the 'can't open file' error message and bring me back to the menu. It prints infinite menus and I have to crash it$.$ Can you please suggest a solution?

#include

#include

#include

#include

#include

#include

using namespace std;

$//$course structure

struct Course $\{$

$$ string courseId;

$$ string title;

$$ vector prerequisites;

$\}$;

$//$function to split a string by a delimiter

vector split$($const string& str$,$ char delimiter$)\{$

$$ vector tokens;

$$ stringstream ss$($str$)$;

$$ string token;

$$ while $($getline$($ss$,$ token, delimiter$))\{$

$$ tokens.push$\_$back$($token$)$;

$\}$

$$ return tokens;

$\}$

$//$function to load course data into hash table

void loadCourses$($const string& filename, unordered$\_$map& courseTable$)\{$

$$ ifstream file$($filename$)$;

$$ if $(!$file.is$\_$open$())\{$

$$ cerr $<<$ "Error: Could not open file" $<<$ endl;

$$ return;

$\}$

$$ string line;

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

$$ vector parts $=$ split$($line$,\text{'},\text{'})$;

$$ if $($parts$.$size$()<2)\{$

$$ cerr $<<$ "Error: Invalid data format in file" $<<$ endl;

$$ continue;

$\}$

$$ Course course;

$$ course.courseId $=$ parts$[0]$;

$$ course.title $=$ parts$[1]$;

$$ for $($size$\_$t i $=2$; i $<$ parts.size$()$; $++$i$)\{$

$$ course.prerequisites.push$\_$back$($parts$[$i$])$;

$\}$

$$ courseTable$[$course$.$courseId$]=$ course;

$\}$

$$ file.close$()$;

$$ cout $<<$ "Courses loaded successfully" $<<$ endl;

$\}$

$//$function to print alphanumeric list of all courses

void printCourseList$($const unordered$\_$map& courseTable$)\{$

$$ vector courseIds;

$$ for $($const auto& entry : courseTable$)\{$

$$ courseIds.push$\_$back$($entry$.$first$)$;

$\}$

$$ sort$($courseIds$.$begin$(),$ courseIds.end$())$;

$$ cout $<<$ "Here is a sample schedule:" $<<$ endl;

$$ for $($const string& courseId : courseIds$)\{$

$$ cout $<<$ courseId $<<","<<$ courseTable.at$($courseId$).$title $<<$ endl;

$\}$

$\}$

$//$function to print specific course and course prerequesites

void printCourse$($const unordered$\_$map& courseTable, const string& courseId$)\{$

$$ auto it $=$ courseTable.find$($courseId$)$;

$$ if $($it $==$ courseTable.end$())\{$

$$ cout $<<$ "Error: Course not found" $<<$ endl;

$$ return;

$\}$

$$ const Course& course $=$ it$->$second;

$$ cout $<<$ course.courseId $<<","<<$ course.title $<<$ endl;

$$ cout $<<$ "Prerequisites: $"$;

$$ if $($course$.$prerequisites.empty$())\{$

$$ cout $<<$ "None";

$\}$

$$ else $\{$

$$ for $($size$\_$t i $=0$; i $<$ course.prerequisites.size$()$; $++$i$)\{$

$$ cout $<<$ course.prerequisites$[$i$]$;

$$ if $($i $<$ course.prerequisites.size$()-1)\{$

$$ cout $<<","$;

$\}$

$\}$

$\}$

$$ cout $<<$ endl;

$\}$

$//$main program

int main$()\{$

$$ unordered$\_$map courseTable;

$$ int choice;

$$ string filename;

$$ cout $<<$ "Welcome to the course planner." $<<$ endl;

$$ do $\{$

$$ cout $<<"$

$1.$ Load Data Structure." $<<$ endl;

$$ cout $<<"2.$ Print Course List." $<<$ endl;

$$ cout $<<"3.$ Print Course." $<<$ endl;

$$ cout $<<"9.$ Exit

$"<<$ endl;

$$ cout $<<$ "What would you like to do$?"<<$ endl;

$$ cin $>>$ choice;

$$ switch $($choice$)\{$

$$ case $1$:

$$ cout $<<$ "Enter the file name: $"$;

$$ cin $>>$ filename;

$$ loadCourses$($filename$,$ courseTable$)$;

$$ break;

$$ case $2$:

$$ if $($courseTable$.$empty$())\{$

$$ cout $<<$ "Error: No data loaded. Please load data structure first." $<<$ endl;

$\}$

$$ else $\{$

$$ printCourseList$($courseTable$)$;

$\}$

$$ break;

$$ case $3$:

$$ if $($courseTable$.$empty$())\{$

$$ cout $<<$ "Error: No data loaded. Please load data structure first." $<<$ endl;

$\}$

$$ else $\{$

$$ string courseId;