Two Sum

Hash map in O(n).

dict complement

Implement `two_sum(nums: list[int], target: int) -> tuple[int,int] | None`.

Return the pair of indices or None.

Constraints

2 ≤ len(nums) ≤ 10^5

Example

>>> two_sum([2, 7, 11, 15], 9)
(0, 1)

18 points ~16 min

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Hints

Store value→index in a dict; check target-value on each element.

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