Two Sum Coding | Dataford Interview Questions

While processing item scores for a Coupang ranking workflow, find two distinct array elements whose values add up to a specified target. Return their indices in ascending order.

Implement two_sum(nums, target) using a hash map. You may assume that every valid input contains exactly one solution, and the same array element cannot be used twice.

Formal Specification

Input: nums, a list of integers, and target, an integer.
Output: A list containing the two zero-based indices [i, j] where i < j and nums[i] + nums[j] == target.
Return an empty list only if no valid pair exists, although valid test inputs always contain one pair.

Constraints

2 <= len(nums) <= 10^4
-10^9 <= nums[i] <= 10^9
-10^9 <= target <= 10^9
Exactly one valid pair exists for official inputs

Function Signature

def two_sum(nums, target):

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