Function $2$: validParentheses$($arr$)$

Given a $($possibly empty$)$ array containing only alphabet letters and parentheses $(,),\{,\},[,],$ determine

if the string is valid.

A string is valid if

$$ Open brackets must be closed by the same type of brackets.

$$ Open brackets must be closed in the correct order.

bool validParentheses$($const std::string& s$)\{$

$//$ TODO: Student to implement

return true; $//$ Placeholder return

$\}$