Description:

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.

Example
Example 1:

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

Solutions:

From Two Sum II

class TwoSum:
    def __init__(self,):
        self.ls = []
        self.sort = False
    """
    @param number: An integer
    @return: nothing
    """
    def add(self, number):
        # write your code here
        self.ls.append(number)
        self.sort = False

    """
    @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
        if not self.sort:
            self.ls.sort()
            self.sort = True
        l = 0
        r = len(self.ls) - 1
        while l < r:
            if self.ls[l] + self.ls[r] < value:
                l += 1
            elif self.ls[l] + self.ls[r] > value:
                r -= 1
            else:
                return True
        return False

Total runtime 1130 ms
Your submission beats 10.00% Submissions!

From Two Sum I

from collections import defaultdict
class TwoSum:
    def __init__(self,):
        self.ls = []
        self.dic = defaultdict(list)
    """
    @param number: An integer
    @return: nothing
    """
    def add(self, number):
        # write your code here
        if len(self.dic[number]) < 2:
            self.ls.append(number)
            self.dic[number].append(len(self.ls))
    """
    @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 n in self.ls:
            if n*2 == value:
                return len(self.dic[n]) == 2
            elif (value-n) in self.dic:
                return True
        return False

Total runtime 822 ms
Your submission beats 56.40% Submissions!

from collections import defaultdict
class TwoSum:
    def __init__(self,):
        self.ls = []
        self.dic = defaultdict(int)
    """
    @param number: An integer
    @return: nothing
    """
    def add(self, number):
        # write your code here
        self.ls.append(number)
        self.dic[number] += 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 n in self.ls:
            if n*2 == value:
                return self.dic[n] >= 2
            elif (value-n) in self.dic:
                return True
        return False

Total runtime 670 ms
Your submission beats 96.80% Submissions!