CodeEasy v0.1

Two Sum

Easy Subject: Arrays & Hashing
Time Complexity
O(N)
Space Complexity
O(N)

Problem Description

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

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

Optimal Solution

Python 
def twoSum(nums, target):
    # Store value mapping to its index
    seen = {}
    for i, num in enumerate(nums):
        diff = target - num
        if diff in seen:
            return [seen[diff], i]
        seen[num] = i
    return []