The following is a function to check if the parentheses of a given expression are balanced:

bool areparentheseslalanced const stdistring espression? $($f$.$

tinkeal iststeckechar: charstack;

char ch $=$ expression$[$i$]$;

charsteck, push$($ch$)$;

if $($charstack$.$ istipty$())$ if

return false: $//$ Unotched closing porenthesis

char topchor $-$ chorstack.petk$()$;

charstack, pop$()$;

if $($ch $-\text{'})\text{'}$ is topchar $1-\text{'}(\text{'})$ II

$($ch $=-"]\text{'}85$ topChor $1=\text{'}[")$ il

return false; $//$ Misatched parentheses

$!$

retwn charSteck.isEmoty $0$ :

$1$

Given an expression$-$

write down the contents for all iterations.

content after iteration $1.$

content after iteration $2.$

content after iteration $3.$