Day-12 Insert Delete GetRandom

class RandomizedSet {

    /** Initialize your data structure here. */
    ArrayList<Integer> num=null;
    HashMap<Integer,Integer> map=null;
    java.util.Random rand=new java.util.Random();
    public RandomizedSet() {
        map=new HashMap<>();
        num=new ArrayList<>();
    }
    
    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
    public boolean insert(int val) {
        if(map.containsKey(val)){
            return false;
        }
        else{
            map.put(val,num.size());
            num.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(map.containsKey(val)){
            int index=map.get(val);
            if(index<num.size()-1){
                int last=num.get(num.size()-1);
                num.set(index,last);
                map.put(last,index);
            }
            
            num.remove(num.size()-1);
            map.remove(val);
            System.out.println(num);
            return true;
        }
        
        return false;
    }
    
    /** Get a random element from the set. */
    public int getRandom() {
        return num.get(rand.nextInt(num.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();
 */