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Two Sum Without Nested Loops

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Your question is Two Sum Without Nested Loops. Start with the requirements on the right.

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Problem

An Ancestry Marketing campaign assigns an integer score to each audience segment. Given a list of scores and a target total, find the indices of two distinct segments whose scores add up to the target.

Design an algorithm that avoids two nested loops and runs in linear time on average. Return the indices in ascending order. Each input is guaranteed to contain exactly one valid pair.

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 same element cannot be used twice.

Constraints

  • 2 <= len(nums) <= 10^4
  • -10^9 <= nums[i] <= 10^9
  • -10^9 <= target <= 10^9
  • Exactly one valid pair exists
  • The returned indices must be distinct and in ascending order

Function Signature

def two_sum(nums, target):
Your solutionPython 3
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