[LeetCode][python3]Day28. First Unique Number (30-Day LeetCoding Challenge)

30 days! Lets go Lets go!
N2I -2020.04.28

1. My solution

class FirstUnique:
    
    def __init__(self, nums: List[int]):
        self.queue=set()
        self.uni=OrderedDict()
        for i in nums:
            self.add(i)
    
    def showFirstUnique(self) -> int:
        return next(iter(self.uni.items()))[0] if self.uni else -1
    
    def add(self, value: int) -> None:
        if value not in self.queue:
            self.uni[value]=True
            self.queue.add(value)
        elif value in self.uni:
            del self.uni[value]
        #print(self.queue,self.uni)

Explanation:

If you use an array instead of OrderedDict to record the unique sequence, you will meet time limit in some large test cases.

2. A better Solution

class FirstUnique:
    
    def __init__(self, nums: List[int]):
        self.c = Counter(nums)
        self.d = deque(nums)
    
    def showFirstUnique(self) -> int:
        while self.d and self.c[self.d[0]] != 1: 
            self.d.popleft()
        return self.d[0] if self.d else -1
            
    def add(self, value: int) -> None:
        self.c[value] += 1
        self.d.append(value)

Explanation:

The solution use collections.Counter and collections.deque to find the result.