LeetCode in Racket

78. Subsets

Medium

Given an integer array nums of unique elements, return all possible subsets (the power set).

The solution set must not contain duplicate subsets. Return the solution in any order.

Example 1:

Input: nums = [1,2,3]

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

Example 2:

Input: nums = [0]

Output: [[],[0]]

Constraints:

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

Solution

(define/contract (subset-recur nums ans)
  (-> (listof exact-integer?) (listof (listof exact-integer?)) (listof (listof exact-integer?)))
   (cond [(empty? nums) ans]
         [else (let ([curr (map (lambda (x) (cons (first nums) x)) ans)])
    (subset-recur (rest nums) (append ans curr)))]))

(define/contract (subsets nums)
  (-> (listof exact-integer?) (listof (listof exact-integer?)))
  (subset-recur nums (list empty)))

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