is there any clever way to do that ? my best way was:
object next = list.get(0) ;
list.remove(0) ;
list.add(next) ;
if not is there any type of collection that will make that easier ? I don't like the need of a temporary object to store the element i want to move ..
EDIT: I have tested the propositions listed below, with my code:
long starttime = System.nanoTime() ;
for (int i = 0; i < ntours; i++){
profit += retrieveGroupsWillPlay(groups, ngroups, limit) ;
}
long endtime = System.nanoTime() ;
System.out.println("Timing: " + (endtime - starttime)) ;
System.out.println("Profit: " + profit) ;
here is the results: (profit: 15, ensure that the result is right for my code) code:
private static int retrieveGroupsWillPlay(ArrayList<Integer> queue,int ngroups, int limit) {
int peopleWillPlay = 0 ;
for (int i = 0; i < ngroups; i++){
int nextGroup = queue.get(0) ;
if(limit >= peopleWillPlay + nextGroup) {
peopleWillPlay += nextGroup ;
queue.add(nextGroup) ;
queue.remove(0) ;
}
else break ;
}
return peopleWillPlay ;
}
results:
Timing: 23326
Profit: 15
Timing: 22171
Profit: 15
Timing: 22156
Profit: 15
Timing: 22944
Profit: 15
Timing: 22240
Profit: 15
Timing: 21769
Profit: 15
Timing: 21866
Profit: 15
Timing: 22341
Profit: 15
Timing: 24049
Profit: 15
Timing: 22420
Profit: 15
code:
private static int retrieveGroupsWillPlay(ArrayList<Integer> queue,int ngroups, int limit) {
int peopleWillPlay = 0 ;
for (int i = 0; i < ngroups; i++){
int nextGroup = queue.get(0) ;
if(limit >= peopleWillPlay + nextGroup) {
peopleWillPlay += nextGroup ;
Collections.rotate(queue, -1) ;
}
else break ;
}
return peopleWillPlay ;
}
results:
Timing: 92101
Profit: 15
Timing: 87137
Profit: 15
Timing: 84531
Profit: 15
Timing: 105919
Profit: 15
Timing: 77019
Profit: 15
Timing: 84805
Profit: 15
Timing: 93393
Profit: 15
Timing: 77079
Profit: 15
Timing: 84315
Profit: 15
Timing: 107002
Profit: 15
code:
private static int retrieveGroupsWillPlay(ArrayList<Integer> queue,int ngroups, int limit) {
int peopleWillPlay = 0 ;
for (int i = 0; i < ngroups; i++){
int nextGroup = queue.get(0) ;
if(limit >= peopleWillPlay + nextGroup) {
peopleWillPlay += nextGroup ;
queue.add(queue.remove(0)) ;
}
else break ;
}
return peopleWillPlay ;
}
results:
Timing: 28079
Profit: 15
Timing: 28994
Profit: 15
Timing: 29525
Profit: 15
Timing: 22240
Profit: 15
Timing: 38326
Profit: 15
Timing: 33742
Profit: 15
Timing: 21500
Profit: 15
Timing: 22714
Profit: 15
Timing: 20939
Profit: 15
Timing: 30157
Profit: 15
code:
private static int retrieveGroupsWillPlay(LinkedList<Integer> queue,int ngroups, int limit) {
int peopleWillPlay = 0 ;
for (int i = 0; i < ngroups; i++){
int nextGroup = queue.get(0) ;
if(limit >= peopleWillPlay + nextGroup) {
peopleWillPlay += nextGroup ;
queue.addLast(queue.removeFirst()) ;
}
else break ;
}
return peopleWillPlay ;
}
result:
Timing: 31104
Profit: 15
Timing: 42332
Profit: 15
Timing: 36443
Profit: 15
Timing: 31840
Profit: 15
Timing: 31387
Profit: 15
Timing: 32102
Profit: 15
Timing: 31347
Profit: 15
Timing: 30666
Profit: 15
Timing: 32781
Profit: 15
Timing: 32464
Profit: 15
code:
private static int retrieveGroupsWillPlay(LinkedList<Integer> queue,int ngroups, int limit) {
int peopleWillPlay = 0 ;
for (int i = 0; i < ngroups; i++){
int nextGroup = queue.get(0) ;
if(limit >= peopleWillPlay + nextGroup) {
peopleWillPlay += nextGroup ;
queue.offer(queue.poll()) ;
}
else break ;
}
return peopleWillPlay ;
}
results:
Timing: 35389
Profit: 15
Timing: 34849
Profit: 15
Timing: 43606
Profit: 15
Timing: 41796
Profit: 15
Timing: 51122
Profit: 15
Timing: 59302
Profit: 15
Timing: 32340
Profit: 15
Timing: 35654
Profit: 15
Timing: 34586
Profit: 15
Timing: 35479
Profit: 15
You can use Collections.rotate
for that:
Collections.rotate(list, -1);
I'm not exactly sure what you want to do, but here goes:
If you're using something like an ArrayList
, you can do:
list.add(list.remove(0));
Please keep in mind that remove
from an ArrayList runs in linear time, that is, O(N)
, so that is extremely inefficient.
In case you can choose the type of List, you probably want a LinkedList
, that implementes the Dequeue
interface, so it would allow you to do something like:
list.offer(list.poll());
Both offer
and poll
are operations done in constant time.
If you want to use a builtin from the Collections
class, you can do as @dasblinkenlight suggested and use Collections.rotate(list, -1);
(adding it here for completeness).
You don't need a temp variable just write:
list.add(list.remove(0));
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