LeetCode 1429 First Unique Number - Medium

1429. First Unique Number — Medium

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Problem

1429. First Unique Number -- Medium

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: ["FirstUnique","showFirstUnique","add","showFirstUnique","add","showFirstUnique","add","showFirstUnique"] [[[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: ["FirstUnique","showFirstUnique","add","add","add","add","add","showFirstUnique"] [[[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: ["FirstUnique","showFirstUnique","add","showFirstUnique"] [[[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

from collections import OrderedDict        
class FirstUnique:
    def __init__(self, nums: List[int]):
        self.unique_nums = OrderedDict()
        self.added_nums = set()
        for num in nums:
            self.add(num)
    def showFirstUnique(self) -> int:
        # if unique_nums is not empty, return the first key in it. 
        for num in self.unique_nums.keys():
            return num
        return -1
    def add(self, value: int) -> None:
        if value in self.added_nums:
            if value in self.unique_nums:
                del self.unique_nums[value]
        else:
            self.added_nums.add(value)
            self.unique_nums[value] = None
 
 
# Your FirstUnique object will be instantiated and called as such:
# obj = FirstUnique(nums)
# param_1 = obj.showFirstUnique()
# obj.add(value)