[Swift]LeetCode491. 递增子序列 | Increasing Subsequences

Given an integer array, your task is to find all the different possible increasing subsequences of the given array, and the length of an increasing subsequence should be at least 2 .

Example:

Input: [4, 6, 7, 7]
Output: [[4, 6], [4, 7], [4, 6, 7], [4, 6, 7, 7], [6, 7], [6, 7, 7], [7,7], [4,7,7]] 

Note:

1. The length of the given array will not exceed 15.
2. The range of integer in the given array is [-100,100].
3. The given array may contain duplicates, and two equal integers should also be considered as a special case of increasing sequence.

示例:

输入: [4, 6, 7, 7]
输出: [[4, 6], [4, 7], [4, 6, 7], [4, 6, 7, 7], [6, 7], [6, 7, 7], [7,7], [4,7,7]]

说明:

1. 给定数组的长度不会超过15。
2. 数组中的整数范围是 [-100,100]。
3. 给定数组中可能包含重复数字，相等的数字应该被视为递增的一种情况。

Memory Usage: 17.3 MB

 1 class Solution {
 2     func findSubsequences(_ nums: [Int]) -> [[Int]] {
 3         var res:Set<[Int]> = Set<[Int]>()
 4         var cur:[[Int]] = [[]]
 5         for i in 0..<nums.count
 6         {
 7             var n:Int = cur.count
 8             for j in 0..<n
 9             {
10                 if !cur[j].isEmpty && cur[j].last! > nums[i]
11                 {
12                     continue
13                 }
14                 cur.append(cur[j])
15                 cur[cur.count - 1].append(nums[i])
16                 if cur[cur.count - 1].count >= 2
17                 {
18                     res.insert(cur.last!)
19                 }
20             }
21         }
22         return [[Int]](res)
23     }
24 }

15810 kb

 1 class Solution {
 2     func findSubsequences(_ nums: [Int]) -> [[Int]] {
 3         guard nums.count > 0 else { return [[Int]]() }
 4
 5         var visit = [Bool](repeating: false, count: nums.count)
 6         var res = [[Int]]()
 7
 8         dfs(nums, 0, &res, &visit, getPrev(nums), [Int]())
 9
10         return res
11     }
12
13     private func dfs(_ nums: [Int], _ index: Int, _ res: inout [[Int]], _ visit: inout [Bool], _ prev: [Int], _ list: [Int]) {
14         if list.count > 1 {
15             res.append(list)
16         }
17
18         var list = list
19
20         for i in index..<nums.count {
21             if index >= 1, nums[i] < nums[index-1] {
22                 continue
23             }
24
25             if prev[i] != -1, visit[prev[i]] == false, (list.count == 0 || prev[i] > index-1) {
26                 continue
27             }
28
29             list.append(nums[i])
30             visit[i] = true
31             dfs(nums, i+1, &res, &visit, prev, list)
32             visit[i] = false
33             list.removeLast()
34         }
35     }
36
37     private func getPrev(_ nums: [Int]) -> [Int] {
38         var map = [Int: Int]()
39         var prev = [Int](repeating: -1, count: nums.count)
40
41         for i in 0..<nums.count {
42             if let value = map[nums[i]] {
43                 prev[i] = value
44             }
45             map[nums[i]] = i
46         }
47
48         return prev
49     }
50 }

原文地址：https://www.cnblogs.com/strengthen/p/10348625.html