Stack
Hsuan-Tien Lin
Dept. of CSIE, NTU
March 31, 2020
Stack
mimic: “pile of documents” on your desk
Stack: Last-In-First-Out (LIFO) Stack
(constant-time) operations:
• insertTop(data), often called push(data)
• removeTop(), often called pop()
• getTop(), often called peek()
—LIFO: 擠電梯 , 洗盤子
very restricted data structure, but important for computers
—will discuss some cases later
H.-T. Lin (NTU CSIE) Stack 3/19
push 3
push 5
pop -> 5
A Simple Application: Parentheses Balancing
• in C, the following characters show up in pairs: (), [], {}, ""
good: {xxx(xxxxxx)xxxxx"xxxx"x}
bad: {xxx(xxxxxx}xxxxx"xxxx"x}
• the LISP programming language
(append (pow (* (+ 3 5) 2) 4) 3) how can we check parentheses balancing?
Stack Solution to Parentheses Balancing
inner-most parentheses pair =⇒ top-most plate
’(’: 堆盤子上去 ; ’)’: 拿盤子下來 Parentheses Balancing Algorithm
for each c in the input do if c is a left character
push c to the stack else if c is a right character
pop d from the stack and check if match end if
end for
many more sophisticated use in compiler design (will see some)
H.-T. Lin (NTU CSIE) Stack 5/19
System Stack
• recall: function call ⇔ 拿新的草稿紙來算
• old (original) scrap paper: temporarily not used, 可以壓在下面 System Stack: 一疊草稿紙 , each paper (stack frame) contains
• return address: where to return to the previous scrap paper
• local variables (including parameters): to be used for calculating within this function
• previous frame pointer: to be used when escaping from this function
some related issues: security attack?
Stacks Implemented on Array
usually: (growable) consecutive array and push/pop at end-of-array
Stacks Implemented on Linked List
usually: singly linked list and push/pop at head
H.-T. Lin (NTU CSIE) Stack 9/19
Stack in STL
1 stack < i n t , vector <i n t> > s_on_array ;
2 stack < i n t , l i s t <i n t> > s_on_array ; implemented as containeradapter
