Hackathon_Java_tasks/QueueusingStack.java at DSA · prathamesh424/Hackathon_Java_tasks · 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
import java.util.Stack;

public class QueueusingStack {
    private Stack<Integer> first ;
    private Stack<Integer> second ;

public QueueusingStack(){
    first = new Stack<>();
    second= new Stack<>();

}
public void add(int number){
    first.push(number);
}

public int  remove () throws Exception{
    while (!first.isEmpty()){
        second.push(first.pop());
    }

    int removed = second.pop();
    while(!second.isEmpty()){
        first.push(second.pop());
    }
    return removed ;
}

public int peek () throws Exception {
     while (!first.isEmpty()){
        second.push(first.pop());
    }
    int peeked = second.peek();

    while(!second.isEmpty()){
        first.push(second.pop());
    }
    return peeked ;
}

public boolean isEmpty () {
    return first.isEmpty() ;
}
}