lintcode练习-607. Two Sum III - Data structure design

描述

设计b并实现一个 TwoSum 类。他需要支持以下操作:add 和 find。
add -把这个数添加到内部的数据结构。
find -是否存在任意一对数字之和等于这个值

您在真实的面试中是否遇到过这个题？  是

样例

add(1);add(3);add(5);
find(4)//返回true
find(7)//返回false

实现代码：

两个思路，因为在意位置信息，所以直接用字典来存储；或者用列表存储

class TwoSum:
    def __init__(self):
        self.counts = {}
    """
    @param: number: An integer
    @return: nothing
    """
    def add(self, number):
        # write your code here
        self.counts[number] = self.counts.get(number, 0) + 1

    """
    @param: value: An integer
    @return: Find if there exists any pair of numbers which sum is equal to the value.
    """
    def find(self, value):
        # write your code here
        for num in self.counts:
            if value - num in self.counts:
                #增加判断，当value是2的倍数时，会出现误判：[2, 3] 4，而[2,2 ,3]则没有问题
                if num != value - num or self.counts[num] > 1:
                    return True
        return False


    #--------------------------------------
    def __init__(self):
        self.nums = []

    """
    @param: number: An integer
    @return: nothing
    """

    def add(self, number):
        # write your code here
        self.nums.append(number)

    """
    @param: value: An integer
    @return: Find if there exists any pair of numbers which sum is equal to the value.
    """

    def find(self, value):
        # write your code here
        _hash = {}
        for i in self.nums:
            if value - i in _hash:
                return True
            _hash[i] = i
        return False