1_TwoSum.py

"""
Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
"""

# leverage a hash table (dictionary) to store numbers we’ve seen so far and quickly check if their complement exists.

class Solution:
    def twoSum(self, nums, target):
        h = {}
        for i, num in enumerate(nums):
            n = target - num
            if n not in h:
                h[num] = i
            else:
                print ([h[n], i])
ex1 = Solution()
ex1.twoSum([2,7,11,15],13)