"""
Given an array of integers, return indices of the two numbers such that they add up to
a specific target.

You may assume that each input would have exactly one solution, and you may not use the
same element twice.

Example:
Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
"""
from __future__ import annotations


def two_sum(nums: list[int], target: int) -> list[int]:
 """
 >>> two_sum([2, 7, 11, 15], 9)
 [0, 1]
 >>> two_sum([15, 2, 11, 7], 13)
 [1, 2]
 >>> two_sum([2, 7, 11, 15], 17)
 [0, 3]
 >>> two_sum([7, 15, 11, 2], 18)
 [0, 2]
 >>> two_sum([2, 7, 11, 15], 26)
 [2, 3]
 >>> two_sum([2, 7, 11, 15], 8)
 []
 >>> two_sum([3 * i for i in range(10)], 19)
 []
 """
 chk_map: dict[int, int] = {}
 for index, val in enumerate(nums):
 compl = target - val
 if compl in chk_map:
 return [chk_map[compl], index]
 chk_map[val] = index
 return []


if __name__ == "__main__":
 import doctest

 doctest.testmod()
 print(f"{two_sum([2, 7, 11, 15], 9) = }")