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380.java
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380.java
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class RandomizedSet {
private Map<Integer, Integer> valueToIndex = new HashMap<>();
private List<Integer> valuesList = new ArrayList<>();
private Random rand = new Random();
private int getLastFromList(List<Integer> valuesList) {
return valuesList.get(valuesList.size()-1);
}
public boolean insert(int val) {
if(valueToIndex.containsKey(val)){
return false;
}
valueToIndex.put(val, valuesList.size());
valuesList.add(val);
return true;
}
public boolean remove(int val) {
if(!valueToIndex.containsKey(val)){
return false;
}
int index = valueToIndex.get(val);
valueToIndex.put(getLastFromList(valuesList), index);
valuesList.set(index, getLastFromList(valuesList));
valueToIndex.remove(val);
valuesList.remove(valuesList.size()-1);
return true;
}
public int getRandom() {
final int index = rand.nextInt(valuesList.size());
return valuesList.get(index);
}
}