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➤微信公众号&＃xff1a;山青咏芝&＃xff08;shanqingyongzhi&＃xff09;
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Given a set of distinct integers, nums, return all possible subsets (the power set).
Note: The solution set must not contain duplicate subsets.
Example:
Input: nums &＃61; [1,2,3]
Output:
[[3],[1],[2],[1,2,3],[1,3],[2,3],[1,2],[]
]
给定一组不含重复元素的整数数组 nums&＃xff0c;返回该数组所有可能的子集&＃xff08;幂集&＃xff09;。
说明&＃xff1a;解集不能包含重复的子集。
示例:
输入: nums &＃61; [1,2,3]
输出:
[[3],[1],[2],[1,2,3],[1,3],[2,3],[1,2],[]
]
8ms
1 class Solution {
2 func subsets(_ nums: [Int]) -> [[Int]] {
3 var res &＃61; [[Int]()]
4 subset(&res, nums)
5 return res
6 }
7
8 private func subset(_ res: inout [[Int]], _ nums: [Int]) {
9 guard let n &＃61; nums.first else { return }
10 res &＃43;&＃61; res.map { $0 &＃43; [n] }
11 subset(&res, Array(nums[1..<nums.count]))
12 }
13 }
12ms
1 class Solution {
2 func subsets(_ nums: [Int]) -> [[Int]] {
3 if nums.count &＃61;&＃61; 0 {
4 return []
5 }
6
7 var result &＃61; [[Int]]()
8 var subset &＃61; [Int]()
9 //call backtracking
10 backtracking(nums, &result, &subset, 0)
11 return result
12 }
13
14 func backtracking(_ nums: [Int], _ result: inout [[Int]], _ subset: inout [Int], _ startIndex: Int) {
15 result.append(subset)
16 for i in startIndex..<nums.count {
17 subset.append(nums[i])
18 backtracking(nums, &result, &subset, i &＃43; 1)
19 subset.removeLast()
20 }
21 }
22 }
12ms
1 class Solution {
2 func subsets(_ nums: [Int]) -> [[Int]] {
3 var res &＃61; [[Int]]()
4 rec_subset([Int](), nums, &res)
5 res.append([Int]())
6 return res
7 }
8
9 func rec_subset(_ firstNums: [Int], _ restNum: [Int], _ res: inout [[Int]]) {
10 if restNum.count &＃61;&＃61; 0 {
11 if firstNums.count !&＃61; 0 {
12 res.append(firstNums)
13 }
14 return
15 }
16
17 var tempRestNums &＃61; restNum;
18 var tempFirstNums &＃61; firstNums;
19 let firstVal &＃61; tempRestNums.remove(at: 0)
20 tempFirstNums.append(firstVal)
21 rec_subset(tempFirstNums, tempRestNums, &res)
22
23 var zeroFirstNums &＃61; firstNums;
24 rec_subset(zeroFirstNums, tempRestNums, &res)
25 }
26 }
16ms
1 class Solution {
2 var result &＃61; [[Int]]()
3 func subsets(_ nums: [Int]) -> [[Int]] {
4 let count &＃61; nums.count
5 for i in 0...count {
6 var changeArray &＃61; Array(repeatElement(0, count: i))
7 combine(&changeArray, nums, 0, i, 0, count)
8 }
9 return result
10 }
11
12 func combine(_ combineArray: inout [Int], _ nums: [Int], _ i: Int, _ total: Int, _ j: Int, _ maxJ: Int) {
13 if i &＃61;&＃61; total {
14 result.append(combineArray)
15 return ;
16 }
17
18 for k in j..<maxJ {
19 combineArray[i] &＃61; nums[k]
20 combine(&combineArray, nums, i &＃43; 1, total, k &＃43; 1, maxJ)
21 }
22 }
23 }
16ms
1 class Solution {
2 func subsets(_ nums: [Int]) -> [[Int]] {
3 guard nums.count > 0 else {return []}
4 var subsets &＃61; [[Int]]()
5 subsets.append([])
6
7 for num in nums {
8 subsets &＃43;&＃61; subsets.map{$0 &＃43; [num]}
9 }
10 return subsets
11 }
12 }
28ms
1 class Solution {
2 func subsets(_ nums: [Int]) -> [[Int]] {
3 if nums.isEmpty {
4 return []
5 }
6
7 var res: [[Int]] &＃61; [[]]
8 helper(nums, &res)
9 return res
10 }
11
12 fileprivate func helper(_ nums: [Int], _ res: inout [[Int]]) {
13
14 guard let first &＃61; nums.first else {
15 return
16 }
17
18 res &＃43;&＃61; res.map{$0 &＃43; [first]}
19 helper(Array(nums[1..
20 }
21 }
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