#define MAX$\_$COURSES $100$

#define MAX$\_$NAME$\_$LEN $50$

int graph$\_$courses$[$MAX$\_$COURSES$][$MAX$\_$COURSES$]$;

char courses$[$MAX$\_$COURSES$][$MAX$\_$NAME$\_$LEN$]$;

int num$\_$courses $=0$;

int get$\_$course$\_$index$($char$*$ name$)\{$

for $($int i $=0$; i $<$ num$\_$courses; i$++)\{$

if $($strcmp$($courses$[$i$],$ name$)==0)\{$

return i;

$\}$

$\}$

return $-1$;

$\}$

void add$\_$edge$\_$courses$($char$*$ src$,$ char$*$ dest$)\{$

int src$\_$index $=$ get$\_$course$\_$index$($src$)$;

int dest$\_$index $=$ get$\_$course$\_$index$($dest$)$;

if $($src$\_$index $==-1||$ dest$\_$index $==-1)\{$

printf$("$Error: Invalid edge between $\%$s and $\%$s

$",$ src$,$ dest$)$;

return;

$\}$

graph$\_$courses$[$src$\_$index$][$dest$\_$index$]=1$;

$\}$

void read$\_$courses$\_$from$\_$file$()\{$

char$*$ filename $=$ "courses.txt$"$;

FILE$*$ file $=$ fopen$($filename$,"$r$")$;

if $($file $==$ NULL$)\{$

printf$("$Error: Could not open file $\%$s

$",$ filename$)$;

return;

$\}$

$//$ Initialize graph$\_$courses to all zeros

memset$($graph$\_$courses, $0,$ sizeof$($graph$\_$courses$))$;

char line$[256]$;

while $($fgets$($line$,$ sizeof$($line$),$ file$))\{$

char src$[$MAX$\_$NAME$\_$LEN$],$ dest$1[$MAX$\_$NAME$\_$LEN$],$ dest$2[$MAX$\_$NAME$\_$LEN$]=""$;

int count $=$ sscanf$($line$,"\%[^$#$]$#$\%[^$#$]$#$\%$s$",$ src$,$ dest$1,$ dest$2)$;

if $($count $<2)\{$

printf$("$Error: Invalid line in file: $\%$s

$",$ line$)$;

continue;

$\}$

$//$ Add the course to the courses array if not already present

if $($get$\_$course$\_$index$($src$)==-1)\{$

strcpy$($courses$[$num$\_$courses$++],$ src$)$;

$\}$

$//$ Add the first prerequisite to the courses array if not already present

if $($get$\_$course$\_$index$($dest$1)==-1)\{$

strcpy$($courses$[$num$\_$courses$++],$ dest$1)$;

$\}$

$//$ If there is a second prerequisite, add it to the courses array if not already present

if $($count $==3$ && get$\_$course$\_$index$($dest$2)==-1)\{$

strcpy$($courses$[$num$\_$courses$++],$ dest$2)$;

$\}$

$//$ Add edges only if the prerequisites are valid courses

if $($get$\_$course$\_$index$($src$)!=-1$ && get$\_$course$\_$index$($dest$1)!=-1)\{$

add$\_$edge$\_$courses$($dest$1,$ src$)$;

$\}$

if $($count $==3$ && get$\_$course$\_$index$($dest$2)!=-1)\{$

add$\_$edge$\_$courses$($dest$2,$ src$)$;

$\}$

$\}$

fclose$($file$)$;

$\}$

void topological$\_$sort$()\{$

int in$\_$degree$[$MAX$\_$COURSES$]=\{0\}$;

int queue$[$MAX$\_$COURSES$],$ front $=0,$ rear $=-1$;

int top$\_$order$[$MAX$\_$COURSES$]$;

int counter $=0$;

$//$ Calculate in$-$degree $($number of incoming edges$)$ for each of the vertex present in the graph

for$($int i $=0$; i $<$ num$\_$courses; i$++)$

for$($int j $=0$; j $<$ num$\_$courses; j$++)$

in$\_$degree$[$i$]+=$ graph$\_$courses$[$j$][$i$]$;

$//$ Enqueue all vertices with in$-$degree of $0$

for$($int i $=0$; i $<$ num$\_$courses; i$++)\{$

if$($in$\_$degree$[$i$]==0)\{$

queue$[++$rear$]=$ i;

$\}$

$\}$

while $($front $<=$ rear$)\{$

int u $=$ queue$[$front$++]$;

top$\_$order$[$counter$++]=$ u;

$//$ For each neighbor v of u$,$ if in$-$degree$[$v$]$ becomes $0,$ then enqueue it

for$($int v $=0$; v $<$ num$\_$courses; v$++)\{$

if$($graph$\_$courses$[$u$][$v$])\{$

in$\_$degree$[$v$]--$;

if$($in$\_$degree$[$v$]==0)\{$

queue$[++$rear$]=$ v;

$\}$

$\}$

$\}$

$\}$

$//$ If count of visited nodes is not equal to the number of nodes in the graph then the topological sort is not possible for the given graph

if$($counter $!=$ num$\_$courses$)\{$

printf$("$There exists a cycle in the graph

$")$;

return;

$\}$

$\}$

$//$print the sorted courses

void print$\_$sorted$\_$courses$()\{$

for$($int i $=0$; i $<$ num$\_$courses; i$++)\{$

printf$("\%$s $",$ courses$[$i$])$;

$\}$

printf$("$

$")$;

$\}$

fix the code the output should be :

COMP$133,$ COMP$233,$ COMP$2310,$ COMP$2421,$ ENCS$2340,$ ENCS$3130,$

ENCS$3340,$ ENCS$4320,$ COMP$333,$ ENCS$2380,$ COMP$433,$ ENCS$3310$

and the input file is :

COMP$2310$#COMP$133$

COMP$2421$#COMP$133$

COMP$333$#COMP$2421$

COMP$433$#COMP$333$

ENCS$2340$#COMP$133$

ENCS$2380$#ENCS$2340$

ENCS$3130$#COMP$133$

ENCS$3310$#ENCS$2380$

ENCS$3340$#COMP$233$ and COMP$133$

ENCS$4320$#COMP$233$ and COMP$133$