Python/maths/two_pointer.py
Christian Clauss c909da9b08
pre-commit: Upgrade psf/black for stable style 2023 (#8110)
* pre-commit: Upgrade psf/black for stable style 2023

Updating https://github.com/psf/black ... updating 22.12.0 -> 23.1.0 for their `2023 stable style`.
* https://github.com/psf/black/blob/main/CHANGES.md#2310

> This is the first [psf/black] release of 2023, and following our stability policy, it comes with a number of improvements to our stable style…

Also, add https://github.com/tox-dev/pyproject-fmt and https://github.com/abravalheri/validate-pyproject to pre-commit.

I only modified `.pre-commit-config.yaml` and all other files were modified by pre-commit.ci and psf/black.

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
2023-02-01 18:44:54 +05:30

61 lines
1.5 KiB
Python

"""
Given a sorted array of integers, return indices of the two numbers such
that they add up to a specific target using the two pointers technique.
You may assume that each input would have exactly one solution, and you
may not use the same element twice.
This is an alternative solution of the two-sum problem, which uses a
map to solve the problem. Hence can not solve the issue if there is a
constraint not use the same index twice. [1]
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
[1]: https://github.com/TheAlgorithms/Python/blob/master/other/two_sum.py
"""
from __future__ import annotations
def two_pointer(nums: list[int], target: int) -> list[int]:
"""
>>> two_pointer([2, 7, 11, 15], 9)
[0, 1]
>>> two_pointer([2, 7, 11, 15], 17)
[0, 3]
>>> two_pointer([2, 7, 11, 15], 18)
[1, 2]
>>> two_pointer([2, 7, 11, 15], 26)
[2, 3]
>>> two_pointer([1, 3, 3], 6)
[1, 2]
>>> two_pointer([2, 7, 11, 15], 8)
[]
>>> two_pointer([3 * i for i in range(10)], 19)
[]
>>> two_pointer([1, 2, 3], 6)
[]
"""
i = 0
j = len(nums) - 1
while i < j:
if nums[i] + nums[j] == target:
return [i, j]
elif nums[i] + nums[j] < target:
i = i + 1
else:
j = j - 1
return []
if __name__ == "__main__":
import doctest
doctest.testmod()
print(f"{two_pointer([2, 7, 11, 15], 9) = }")