1. Two Sum

class Solution:
    def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        a_dict = {}
        for i in range (0, len(nums)):
            x = nums[i]
            y = target - nums[i]
            if y in a_dict:
                return (a_dict[y], i)
            else:
                a_dict[x] = i