The challenge
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].
The solution in Python
class Solution: def twoSum(self, nums: List[int], target: int) -> List[int]: # keep a hashmap of items found seen = {} # loop through the nums, with int and value for i, v in enumerate(nums): # set remaining to the target minus the value remaining = target - v # check if the new value is in the hashmap if remaining in seen: # return it and the index return [seen[remaining], i] # otherwise, put it on the map instead seen[v] = i # nothing found, return an empty list return []