1+ import java .util .*;
2+ 3+ class RandomizedSet {
4+ ArrayList <Integer > a ;
5+ Random random ;
6+ public RandomizedSet () {
7+ a = new ArrayList <>();
8+ random = new Random ();
9+ }
10+ public boolean insert (int val ) {
11+ if (a .contains (val )) {
12+ return false ;
13+ }
14+ a .add (val );
15+ return true ;
16+ }
17+ 18+ 19+ public boolean remove (int val ) {
20+ int index = a .indexOf (val );
21+ if (index == -1 ) {
22+ return false ;
23+ }
24+ int lastValue = a .get (a .size () - 1 );
25+ a .set (index , lastValue );
26+ a .remove (a .size () - 1 );
27+ return true ;
28+ }
29+ 30+ 31+ public int getRandom () {
32+ int randomIndex = random .nextInt (a .size ()); //
33+ return a .get (randomIndex );
34+ }
35+ 36+ }
37+ 38+ class Main {
39+ public static void main (String [] args ) {
40+ RandomizedSet randomizedSet = new RandomizedSet ();
41+ 42+ System .out .println (randomizedSet .insert (1 ));
43+ System .out .println (randomizedSet .remove (2 ));
44+ System .out .println (randomizedSet .insert (2 ));
45+ System .out .println (randomizedSet .getRandom ());
46+ System .out .println (randomizedSet .remove (1 ));
47+ System .out .println (randomizedSet .insert (2 ));
48+ System .out .println (randomizedSet .getRandom ());
49+ 50+ }
51+ }
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