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Two Sum Optimized

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Your question is Two Sum Optimized. Start with the requirements on the right.

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Problem

Ancestry may need to identify two values from a list of record-related measurements whose combined value matches a specified target. Given an integer array nums and an integer target, return the indices of two distinct elements whose values add up to target.

Use an optimized approach that does not compare every pair with nested loops. You may assume that each 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.
  • Function: Implement two_sum(nums, target).

Constraints

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

Function Signature

def two_sum(nums, target):
Your solutionPython 3
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