Solve Two Sum | Dataford Interview Questions

Cisco telemetry services may need to identify two measurements whose combined value reaches a specified threshold. Given an unsorted array of integers nums and an integer target, return the indices of two distinct elements whose values add up to target.

Use each array position at most once. Return the pair as [i, j], where i < j. Each valid input contains exactly one solution, so the order of the returned indices is deterministic. Aim for a one-pass solution with better than quadratic time.

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 input array is not sorted, and duplicate values are allowed.

Constraints

2 <= len(nums) <= 100,000
-10^9 <= nums[i] <= 10^9
-10^9 <= target <= 10^9
Exactly one valid pair exists
The two indices must be distinct and returned in increasing order

Function Signature

def two_sum(nums, target):

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