LeetCode-in-All

46. Permutations

Medium

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Example 1:

Input: nums = [1,2,3]

Output: [[1,2,3],[1,3,2],[2,1,3],[2,3,1],[3,1,2],[3,2,1]]

Example 2:

Input: nums = [0,1]

Output: [[0,1],[1,0]]

Example 3:

Input: nums = [1]

Output: [[1]]

Constraints:

• 1 <= nums.length <= 6
• -10 <= nums[i] <= 10
• All the integers of nums are unique.

Solution

-spec permute(Nums :: [integer()]) -> [[integer()]].
permute([Num]) ->
    [[Num]];
permute(Nums) ->
    Permute = fun(Num) ->
        Rest = lists:delete(Num, Nums),
        lists:map(fun(Tail) -> [Num | Tail] end, permute(Rest))
    end,
    lists:append(lists:map(Permute, Nums)).

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