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380.java
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380.java
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public class RandomizedSet {
List<Integer> rand = new ArrayList<>();
Map<Integer, Integer> vi = new HashMap<>();
/** Initialize your data structure here. */
public RandomizedSet() {
}
/** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
public boolean insert(int val) {
if(vi.containsKey(val)) {
return false;
}
vi.put(val, rand.size());
rand.add(val);
return true;
}
/** Removes a value from the set. Returns true if the set contained the specified element. */
public boolean remove(int val) {
if(!vi.containsKey(val)) {
return false;
}
int old = vi.get(val);
int lastVal = rand.get(rand.size() - 1);
rand.set(old, lastVal);
vi.put(lastVal, old);
rand.remove(rand.size() - 1);
vi.remove(val);
return true;
}
/** Get a random element from the set. */
public int getRandom() {
return rand.get((int)(Math.random() * rand.size()));
}
}
/**
* Your RandomizedSet object will be instantiated and called as such:
* RandomizedSet obj = new RandomizedSet();
* boolean param_1 = obj.insert(val);
* boolean param_2 = obj.remove(val);
* int param_3 = obj.getRandom();
*/