170.py

'''
Design and implement a TwoSum class. It should support the following operations: add and find.

add – Add the number to an internal data structure.
find – Find if there exists any pair of numbers which sum is equal to the value.

For example,
add(1); add(3); add(5);
find(4) -> true
find(7) -> false
'''

class TwoSum(object):

    def __init__(self):
        """
        initialize your data structure here
        """
        self.value_count = {}

    def add(self, number):
        """
        Add the number to an internal data structure.
        :rtype: nothing
        """
        if number in self.value_count:
        	self.value_count[number] += 1
        else:
        	self.value_count[number] = 1

    def find(self, value):
        """
        Find if there exists any pair of numbers which sum is equal to the value.
        :type value: int
        :rtype: bool
        """
        for val in self.value_count:
        	diff = value - val
        	if diff in self.value_count and (diff != val or self.value_count[val] > 1):
        		return True
        return False

# Your TwoSum object will be instantiated and called as such:
# twoSum = TwoSum()
# twoSum.add(number)
# twoSum.find(value)