1(Basic), 2(Infix to postfix), 5(next greater element), 7 (2 Stack in 1 Array), 9 (Stock Span Problem) ,10 (Reverse), 11 (Sort), 12 (Celebrity Problem), 13 & 14 (Design), 16  List of questions on GeekForGeeks Always use the methods defined for Stack Collection whenever possible. Like to check if the stack is empty or not use… Continue reading Stack