forked from TheAlgorithms/Java
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathStacks.java
More file actions
207 lines (184 loc) · 4.59 KB
/
Stacks.java
File metadata and controls
207 lines (184 loc) · 4.59 KB
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
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
import java.util.ArrayList;
/**
* This class implements a Stack using two different implementations.
* Stack is used with a regular array and Stack2 uses an ArrayList.
*
* A stack is exactly what it sounds like. An element gets added to the top of
* the stack and only the element on the top may be removed. This is an example
* of an array implementation of a Stack. So an element can only be added/removed
* from the end of the array. In theory stack have no fixed size, but with an
* array implementation it does.
*
* @author Unknown
*
*/
class Stack{
/** The max size of the Stack */
private int maxSize;
/** The array representation of the Stack */
private int[] stackArray;
/** The top of the stack */
private int top;
/**
* Constructor
*
* @param size Size of the Stack
*/
public Stack(int size){
maxSize = size;
stackArray = new int[maxSize];
top = -1;
}
/**
* Adds an element to the top of the stack
*
* @param value The element added
*/
public void push(int value){
top++;
stackArray[top] = value;
}
/**
* Removes the top element of the stack and returns the value you've removed
*
* @return value popped off the Stack
*/
public int pop(){
return stackArray[top--];
}
/**
* Returns the element at the top of the stack
*
* @return element at the top of the stack
*/
public int peek(){
return stackArray[top];
}
/**
* Returns true if the stack is empty
*
* @return true if the stack is empty
*/
public boolean isEmpty(){
return(top == -1);
}
/**
* Returns true if the stack is full
*
* @return true if the stack is full
*/
public boolean isFull(){
return(top+1 == maxSize);
}
/**
* Deletes everything in the Stack
*
* Doesn't delete elements in the array
* but if you call push method after calling
* makeEmpty it will
A1E0
overwrite previous
* values
*/
public void makeEmpty(){ //Doesn't delete elements in the array but if you call
top = -1; //push method after calling makeEmpty it will overwrite previous values
}
}
/**
* This is an ArrayList Implementation of stack, Where size is not
* a problem we can extend the stack as much as we want.
*
* @author Unknown
*
*/
class Stack2{
/** ArrayList representation of the stack */
ArrayList<Integer> stackList;
/**
* Constructor
*/
Stack2(){
stackList=new ArrayList<>();
}
/**
* Adds value to the end of list which
* is the top for stack
*
* @param value value to be added
*/
void push(int value){
stackList.add(value);
}
/**
* Pops last element of list which is indeed
* the top for Stack
*
* @return Element popped
*/
int pop(){
if(!isEmpty()){ // checks for an empty Stack
int popValue=stackList.get(stackList.size()-1);
stackList.remove(stackList.size()-1); //removes the poped element from the list
return popValue;
}
else{
System.out.print("The stack is already empty ");
return -1;
}
}
/**
* Checks for empty Stack
*
* @return true if stack is empty
*/
boolean isEmpty(){
if(stackList.isEmpty())
return true;
else return false;
}
/**
* Top element of stack
*
* @return top element of stack
*/
int peek(){
return stackList.get(stackList.size()-1);
}
}
/**
* This class implements the Stack and Stack2 created above
*
* @author Unknown
*
*/
public class Stacks{
/**
* Main method
*
* @param args Command line arguments
*/
public static void main(String args[]){
Stack myStack = new Stack(4); //Declare a stack of maximum size 4
//Populate the stack
myStack.push(5);
myStack.push(8);
myStack.push(2);
myStack.push(9);
System.out.println("*********************Stack Array Implementation*********************");
System.out.println(myStack.isEmpty()); //will print false
System.out.println(myStack.isFull()); //will print true
System.out.println(myStack.peek()); //will print 9
System.out.println(myStack.pop()); //will print 9
System.out.println(myStack.peek()); // will print 2
Stack2 myStack2 = new Stack2(); //Declare a stack of maximum size 4
//Populate the stack
myStack2.push(5);
myStack2.push(8);
myStack2.push(2);
myStack2.push(9);
System.out.println("*********************Stack List Implementation*********************");
System.out.println(myStack2.isEmpty()); //will print false
System.out.println(myStack2.peek()); //will print 9
System.out.println(myStack2.pop()); //will print 9
System.out.println(myStack2.peek()); // will print 2
System.out.println(myStack2.pop()); //will print 2
}
}