LeetCoding Challenge 28/30. First Unique Number

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题目

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:

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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:

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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:

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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.

思路

利用dict去重即可。
奇怪的是此题有一个疑似Bug??? here

代码

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class FirstUnique(object):

    def __init__(self, nums):
        """
        :type nums: List[int]
        """
        self.dict = {}
        self.unique_nums = []
        for num in nums:
            if num in self.dict:
                if self.dict[num] == 1:
                    self.unique_nums.remove(num)
                self.dict[num] += 1
            else:
                self.unique_nums.append(num)
                self.dict[num] = 1

    def showFirstUnique(self):
        """
        :rtype: int
        """
        if self.unique_nums:
            return self.unique_nums[0]
        else:
            return -1

    def add(self, value):
        """
        :type value: int
        :rtype: None
        """
        if value in self.dict:
            if self.dict[value] == 1:
                self.unique_nums.remove(value)
            self.dict[value] += 1
        else:
            self.unique_nums.append(value)
            self.dict[value] = 1


# Your FirstUnique object will be instantiated and called as such:
# obj = FirstUnique(nums)
# param_1 = obj.showFirstUnique()
# obj.add(value)