hacktoberfest2020/stack.java at master · mukund-create/hacktoberfest2020 · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
A stack is an Abstract Data Type (ADT), commonly used in most programming languages. It is named stack as it behaves like a real-world stack, for example – a deck of cards or a pile of plates, etc.

Stack operations may involve initializing the stack, using it and then de-initializing it. Apart from these basic stuffs, a stack is used for the following two primary operations −


 1)push() − Pushing (storing) an element on the stack.

  A simple algorithm for Push operation can be derived as follows −

begin procedure push: stack, data

   if stack is full
      return null
   endif

   top ← top + 1
   stack[top] ← data

end procedure


 2)pop() − Removing (accessing) an element from the stack.
A simple algorithm for Pop operation can be derived as follows −

begin procedure pop: stack

   if stack is empty
      return null
   endif

   data ← stack[top]
   top ← top - 1
   return data

end procedure


When data is PUSHed onto stack.

To use a stack efficiently, we need to check the status of stack as well. For the same purpose, the following functionality is added to stacks −


 3)peek() − get the top data element of the stack, without removing it.

 Algorithm of peek() function −

begin procedure peek
   return stack[top]
end procedure


 4)isFull() − check if stack is full.

  Algorithm of isfull() function −

begin procedure isfull

   if top equals to MAXSIZE
      return true
   else
      return false
   endif

end procedure


 5)isEmpty() − check if stack is empty.

  Algorithm of isempty() function −

begin procedure isempty

   if top less than 1
      return true
   else
      return false
   endif

end procedure