There is a tets file which gives the expected output and the code proposed by the epxert is not providing that: import school$\_$group$\_$separation

def verifyAns$($fileNameInput$,$ fileNameOutput, ExpectedAnswer$)$:

fileOut $=$ open$($fileNameOutput$,"$r$")$

linesOut $=$ fileOut.readlines$()$

fileOut.close$()$

if$($not ExpectedAnswer$)$:

if$($linesOut$[0].$strip$()!=$ "impossible"$)$:

raise Exception$("$Wrong answer, should be $\backslash "$impossible$\backslash "")$

else:

fileIn $=$ open$($fileNameInput$,"$r$")$

linesIn $=$ fileIn.readlines$()$

fileIn.close$()$

nbStudents $=$ int$($linesIn$[0])$

students $=[]$

if$($nbStudents $!=0)$:

students $=[$s$.$strip$()$ for s in linesIn$[1$:nbStudents$+1]]$

nbPairs $=$ int$($linesIn$[$nbStudents$+1])$

pairs $=[]$

if$($nbPairs $!=0)$:

pairs $=$ linesIn$[$nbStudents$+2$:nbStudents$+$nbPairs$+2]$

groupA $=$ set$($linesOut$[0].$strip$().$split$())$

groupB $=$ set$($linesOut$[1].$strip$().$split$())$

#each student is in the answer, and only in one group

for s in students:

if$(($s in groupA$)==($s in groupB$))$:

if$($s in groupA$)$:

raise Exception$("$Student $"+$ str$($s$)+"$ has been put in both groups"$)$

else:

raise Exception$("$Student $"+$ str$($s$)+"$ hasn't been put in any group"$)$

#there are no extra students or duplicate:

if$($len$($groupA$)+$ len$($groupB$)!=$ nbStudents$)$:

raise Exception$("$Number of students in the output is $"+$ str$($len$($groupA$)+$len$($groupB$))+",$ expected $"+$ str$($nbStudents$))$

#for every given pair, the students are in different groups

for p in pairs:

student$1,$ student$2=$ p$.$strip$().$split$()$

if$(($student$1$ in groupA and student$2$ in groupA$)$ or $($student$1$ in groupB and student$2$ in groupB$))$:

raise Exception$("$Students $"+$ str$($student$1)+"$ and $"+$ str$($student$2)+"$ cannot be in the same group"$)$

if $\_\_$name$\_\_==\text{'}\_\_$main$\_\_\text{'}$:

expected $=[$True$,$ False, True, False, False, True, True, True, False, True, False$]$

for i in range$($len$($expected$))$:

try:

fileIn $=$ "input" $+$ str$($i$)+".$txt$"$

fileOut $=$ "output" $+$ str$($i$)+".$txt$"$

school$\_$group$\_$separation.main$([$fileIn$,$ fileOut$])$

verifyAns$($fileIn$,$ fileOut, expected$[$i$])$

print$("$Test $"+$ str$($i$)+"$ OK

$")$

except Exception as e:

print$("$Test $"+$ str$($i$)+"$ Fail"$)$

print$($e$)$

print$()$