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

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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.

---

给定一个整型数组, 你的任务是找到所有该数组的递增子序列，递增子序列的长度至少是2。

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。

---

Runtime: 472 ms

Memory Usage: 17.3 MB

class Solution {
    func findSubsequences(_ nums: [Int]) -> [[Int]] {
        var res:Set<[Int]> = Set<[Int]>()
        var cur:[[Int]] = [[]]
        for i in 0..<nums.count
        {
            var n:Int = cur.count
            for j in 0..<n
            {
                if !cur[j].isEmpty && cur[j].last! > nums[i]
                {
                    continue
                }
                cur.append(cur[j])
                cur[cur.count - 1].append(nums[i])
                if cur[cur.count - 1].count >= 2
                {
                    res.insert(cur.last!)
                }
            }
        }
        return [[Int]](res)
    }
}

---

15810 kb

class Solution {
    func findSubsequences(_ nums: [Int]) -> [[Int]] {
        guard nums.count > 0 else { return [[Int]]() }
        
        var visit = [Bool](repeating: false, count: nums.count)
        var res = [[Int]]()
        
        dfs(nums, 0, &res, &visit, getPrev(nums), [Int]())
        
        return res
    }
    
    private func dfs(_ nums: [Int], _ index: Int, _ res: inout [[Int]], _ visit: inout [Bool], _ prev: [Int], _ list: [Int]) {
        if list.count > 1 {
            res.append(list)
        }
        
        var list = list
        
        for i in index..<nums.count {
            if index >= 1, nums[i] < nums[index-1] {
                continue
            }
            
            if prev[i] != -1, visit[prev[i]] == false, (list.count == 0 || prev[i] > index-1) {
                continue
            } 
            
            list.append(nums[i])
            visit[i] = true
            dfs(nums, i+1, &res, &visit, prev, list)
            visit[i] = false
            list.removeLast()
        }
    }
    
    private func getPrev(_ nums: [Int]) -> [Int] {
        var map = [Int: Int]()
        var prev = [Int](repeating: -1, count: nums.count)
        
        for i in 0..<nums.count {
            if let value = map[nums[i]] {
                prev[i] = value
            } 
            map[nums[i]] = i
        }
        
        return prev
    }
}