HàPhan 河

First Unique Number

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

Implement the `FirstUnique` class:

• `FirstUnique(int[] nums)` Initializes the object with the numbers in the queue.
• `int showFirstUnique()` returns the value of the first unique integer of the queue, and returns `-1` if there is no such integer.
• `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 <= nums.length <= 10^5`
• `1 <= nums[i] <= 10^8`
• `1 <= value <= 10^8`
• At most `50000` calls will be made to `showFirstUnique` and add.

Solution

It's similar to LRU cache
Use a hash table and a Doubly Linked List

``````class FirstUnique {
private var count = [Int: Int]()
private var nodes = [Int: Node]()

private var firstNode: Node?
private var lastNode: Node?

init(_ nums: [Int]) {
for val in nums {
}
}

func showFirstUnique() -> Int {
if let node = firstNode {
return node.val
}
return -1
}

count[value] = (count[value] ?? 0) + 1

if count[value] == 1 {
var node = Node(value)
lastNode?.next = node
node.prev = lastNode
lastNode = node

if nodes.count == 0 {
firstNode = node
}

nodes[value] = node
}else{
var node = nodes[value]

if firstNode == node {
firstNode = node?.next
}

if lastNode == node {
lastNode = node?.prev
}

node?.prev?.next = node?.next
node?.next?.prev = node?.prev

nodes[value] = nil
}
}
}

class Node : Equatable {
let val: Int
var next: Node?
var prev: Node?

init(_ val: Int) {
self.val = val
}

static func ==(lhs: Node, rhs: Node) -> Bool {
return lhs.val == rhs.val
}
}
``````