Find Two Sum Indices

Problem Statement

At Lyft, you are given an integer array and a target value. Return the indices of the two distinct elements whose sum equals the target.

Formal Specification

Implement a function two_sum(nums, target) where:

• nums is a list of integers
• target is an integer
• Return a list of two integers [i, j] such that nums[i] + nums[j] == target
• You may assume exactly one valid answer exists
• You may not use the same element twice
• Return the indices in any order