I've got to write a very short bit of code on a deque, however I'm not sure how to write the code for the methods, if someone could help me with one of the methods, (eg. a method to add an object to the from of the deque) then that would get me started. I'm sure I could manage the rest of the methods, just at the moment I'm pretty stumped.
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Why are you doing this? What is wrong with using one of the standard Deque implementations?Stephen C– Stephen C2009-08-09 05:12:14 +00:00Commented Aug 9, 2009 at 5:12
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2 Answers
Deques are usually implemented as doubly linked lists. You implement a doubly linked list by keeping track of the first and last element in the list and letting each element keep track of its predecessor and successor.
public class Deque<T> {
private class Node {
Node(T value) {
this.value = value;
}
T value;
Node next, prev;
}
private Node first, last;
public void addFront(T value) {
Node oldFirst = first;
first = new Node(value);
// The old first item is now the second item, so its the successor of
// the new first item
first.next = oldFirst;
// if first was null before, that means the deque was empty
// so first and last should both point to the new item
if(oldFirst == null) {
last = first;
} else {
// If there previously was a first element, this element is
// now the second element and its prev field should point to
// the new first item
oldFirst.prev = first;
}
}
}
Comments
I'm not sure exactly what you're after, but the available methods for the Deque are listed in the Javadoc
