lintcode练习-960. First Unique Number in a Stream II

960. First Unique Number in a Stream II

We need to implement a data structure named DataStream. There are two methods required to be implemented:

1. void add(number) // add a new number
2. int firstUnique() // return first unique number

样例

add(1)
add(2)
firstUnique() => 1
add(1)
firstUnique() => 2

注意事项

You can assume that there must be at least one unique number in the stream when calling the firstUnique.

实现思路：

用一个队列和一个hash表，数字依次存入队列，用hash表记录表中数字的个数，每次都从头开始遍历队列，返回第一个first unique。

class DataStream:

    def __init__(self):
        # do intialization if necessary
        self.queue = []
        self.hashmap = {}
          
    """
    @param num: next number in stream
    @return: nothing
    """
    def add(self, num):
        # write your code here
        self.queue.append(num)
        self.hashmap[num] = self.hashmap.get(num, 0) + 1

    """
    @return: the first unique number in stream
    """
    def firstUnique(self):
        # write your code here
        for i in range(len(self.queue)):
            if self.hashmap[self.queue[i]] == 1:
                #只是返回这个数，并不从数组中删除，让没有相同的数加入时，first unique一直是这个数。
                return self.queue[i]
            
        return -1