Two_Sum.py

# Question: Given an array of integers, return indices of the two numbers such that they add up to a specific target.
# Solution: Keep a hashmap with keys of target - num
# Difficulty: Easy
# Time Complexity: O(n)
# Space Complexity: O(n)

from typing import List

def twoSum(nums: List[int], target: int) -> List[int]:
    # Create a hashmap to store numbers we want to look for
    lookingFor = {}

    for i, v in enumerate(nums):
        # If the number we're at is one we're looking for
        # return it's index along with the one in the hashmap
        if v in lookingFor: 
            return [lookingFor[v], i]
        
        # Otherwise we want to remember to look for the (target - current) later 
        lookingFor[target - v] = i