# First Unique Number

#### Created: April 28, 2020 by [lek-tin]

##### Last updated: April 28, 2020

You have a queue of integers, you need to retrieve the first unique integer in the queue.

Implement the `FirstUnique` class:

1. `FirstUnique(int[] nums)` Initializes the object with the numbers in the queue.
2. `int showFirstUnique()` returns the value of the first unique integer of the queue, and returns `-1` if there is no such integer.
3. `void add(int value)` insert value to the queue.

### Example 1

``````Input:
[[[2,3,5]],[],[5],[],[2],[],[3],[]]
Output:
[null,2,null,2,null,3,null,-1]

Explanation:
FirstUnique firstUnique = new FirstUnique([2,3,5]);
firstUnique.showFirstUnique(); // return 2
firstUnique.add(5);            // the queue is now [2,3,5,5]
firstUnique.showFirstUnique(); // return 2
firstUnique.add(2);            // the queue is now [2,3,5,5,2]
firstUnique.showFirstUnique(); // return 3
firstUnique.add(3);            // the queue is now [2,3,5,5,2,3]
firstUnique.showFirstUnique(); // return -1
``````

### Example 2

``````Input:
[[[7,7,7,7,7,7]],[],[7],[3],[3],[7],[17],[]]
Output:
[null,-1,null,null,null,null,null,17]

Explanation:
FirstUnique firstUnique = new FirstUnique([7,7,7,7,7,7]);
firstUnique.showFirstUnique(); // return -1
firstUnique.add(7);            // the queue is now [7,7,7,7,7,7,7]
firstUnique.add(3);            // the queue is now [7,7,7,7,7,7,7,3]
firstUnique.add(3);            // the queue is now [7,7,7,7,7,7,7,3,3]
firstUnique.add(7);            // the queue is now [7,7,7,7,7,7,7,3,3,7]
firstUnique.add(17);           // the queue is now [7,7,7,7,7,7,7,3,3,7,17]
firstUnique.showFirstUnique(); // return 17
``````

### Example 3

``````Input:
[[[809]],[],[809],[]]
Output:
[null,809,null,-1]

Explanation:
FirstUnique firstUnique = new FirstUnique([809]);
firstUnique.showFirstUnique(); // return 809
firstUnique.add(809);          // the queue is now [809,809]
firstUnique.showFirstUnique(); // return -1
``````

#### Constraints:

1. `1 <= nums.length <= 10^5`
2. `1 <= nums[i] <= 10^8`
3. `1 <= value <= 10^8`
4. At most `50000` calls will be made to `showFirstUnique` and add.

### Solution (queue: time limit exceeded)

Java

``````class FirstUnique {
Queue<Integer> queue;
HashMap<Integer, Integer> counter;
int firstUnique;
public FirstUnique(int[] nums) {
counter = new HashMap<>();
for (int num: nums) {
}
}

public int showFirstUnique() {
return queue.peek() != null ? queue.peek() : -1;
}

counter.put(value, counter.getOrDefault(value, 0) + 1);
if (counter.get(value) > 1) {
queue.remove(value);
} else {
}
}
}

/**
* Your FirstUnique object will be instantiated and called as such:
* FirstUnique obj = new FirstUnique(nums);
* int param_1 = obj.showFirstUnique();
*/
``````

Java

``````import java.util.Deque;

class FirstUnique {
HashSet<Integer> garbage;
int firstUnique;
public FirstUnique(int[] nums) {
garbage = new HashSet<>();
for (int num: nums) {
}
}

public int showFirstUnique() {
Set<Map.Entry<Integer, Integer>> entries = lhmap.entrySet();
Iterator<Map.Entry<Integer, Integer>> it = entries.iterator();
return it.hasNext() ? it.next().getKey() : -1;
}

if (garbage.contains(value)) {
return;
}

if (lhmap.getOrDefault(value, 0) == 0) {
lhmap.put(value, 1);
} else {
lhmap.remove(value);