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Q10866.java
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Q10866.java
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package forRank;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.StringTokenizer;
public class Q10866 {
private static class Node{
int value;
Node next;
Node pre;
public Node(int value){
this.value = value;
next = null;
pre = null;
}
}
private static class Deque{
Node front;
Node back;
int size;
public Deque(){
front = null;
back = null;
size = 0;
}
public void pushFront(int X){
Node newNode = new Node(X);
newNode.next = front;
if(front != null)
front.pre = newNode;
front = newNode;
if(back == null)
back = newNode;
size++;
}
public void pushBack(int X){
Node newNode = new Node(X);
newNode.pre = back;
if(back != null)
back.next = newNode;
back = newNode;
if(front == null)
front = newNode;
size++;
}
public int popFront(){
if(front == null)
return -1;
Node temp = front;
front = front.next;
if(front != null)
front.pre = null;
else
back = null;
size--;
return temp.value;
}
public int popBack(){
if(back == null)
return -1;
Node temp = back;
back = temp.pre;
if(back != null)
back.next = null;
else
front = null;
size--;
return temp.value;
}
public int isEmpty(){
if(front == null) //or back == null
return 1;
return 0;
}
public int peekFront(){
if(front == null)
return -1;
return front.value;
}
public int peekBack(){
if(back == null)
return -1;
return back.value;
}
public int getSize(){
return size;
}
}
public static void main(String[] args) throws IOException {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
Deque deque = new Deque();
int N = Integer.parseInt(br.readLine());
for (int i = 0; i < N; i++) {
StringTokenizer st = new StringTokenizer(br.readLine());
switch(st.nextToken()){
case "push_front":
deque.pushFront(Integer.parseInt(st.nextToken()));
break;
case "push_back":
deque.pushBack(Integer.parseInt(st.nextToken()));
break;
case "pop_front":
bw.write(deque.popFront() + "\n");
break;
case "pop_back":
bw.write(deque.popBack() + "\n");
break;
case "size":
bw.write(deque.getSize() + "\n");
break;
case "empty":
bw.write(deque.isEmpty() + "\n");
break;
case "front":
bw.write(deque.peekFront() + "\n");
break;
case "back":
bw.write(deque.peekBack() + "\n");
break;
}
}
br.close();
bw.close();
}
}