Find two numbers that sum to target

Given an integer array nums of length n and an integer target, return the indices (i, j) (0-based) of two distinct elements such that nums[i] + nums[j] == target.

Requirements:

• Return any one valid pair of indices.
• You may assume exactly one valid pair exists.
• The same element cannot be used twice.

Input: nums: int[], target: int

Output: two indices i, j

Constraints (typical):

• 2 <= n <= 1e5
• -1e9 <= nums[k] <= 1e9
• -1e9 <= target <= 1e9