Two Sum in an Array | Dataford Interview Questions

A Wealthfront Automated Investing feature receives an array of integer adjustments and a target total. Return the indices of the two distinct elements whose values add up to target.

Each input has exactly one valid pair, and the same array element cannot be used twice. Return the indices in ascending order. You may return an empty list only as a fallback for invalid inputs outside the stated constraints.

Formal Specification

Implement two_sum(nums, target):

Input: nums, a list of integers, and target, an integer.
Output: a list containing the two zero-based indices whose values sum to target.
The returned indices must refer to distinct elements and be in ascending order.

Design an algorithm that runs in linear time.

Constraints

2 <= len(nums) <= 10^4
-10^9 <= nums[i] <= 10^9
-10^9 <= target <= 10^9
Exactly one valid pair exists
The same element cannot be used twice

Function Signature

def two_sum(nums, target):

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