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  • [Swift]LeetCode996. 正方形数组的数目 | Number of Squareful Arrays

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    ➤微信公众号：山青咏芝（shanqingyongzhi）
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    Given an array A of non-negative integers, the array is squareful if for every pair of adjacent elements, their sum is a perfect square.

    Return the number of permutations of A that are squareful.  Two permutations A1 and A2 differ if and only if there is some index i such that A1[i] != A2[i]. 

    Example 1:

    Input: [1,17,8]
Output: 2
Explanation: 
[1,8,17] and [17,8,1] are the valid permutations.

    Example 2:

    Input: [2,2,2]
Output: 1 

    Note:

    1. 1 <= A.length <= 12
    2. 0 <= A[i] <= 1e9

    给定一个非负整数数组 A，如果该数组每对相邻元素之和是一个完全平方数，则称这一数组为正方形数组。

    返回 A 的正方形排列的数目。两个排列 A1 和 A2 不同的充要条件是存在某个索引 i，使得 A1[i] != A2[i]。 

    示例 1：

    输入：[1,17,8]
输出：2
解释：
[1,8,17] 和 [17,8,1] 都是有效的排列。

    示例 2：

    输入：[2,2,2]
输出：1 

    提示：

    1. 1 <= A.length <= 12
    2. 0 <= A[i] <= 1e9
    Runtime: 8 ms
    Memory Usage: 18.9 MB
     1 class Solution {
 2     var ans:Int = 0
 3     func numSquarefulPerms(_ A: [Int]) -> Int {
 4         var A = A
 5         ans = 0
 6         dfs(&A,0)
 7         return ans        
 8     }
 9     
10     func dfs(_ A:inout [Int],_ k:Int)
11     {
12         var n:Int = A.count
13         if k == n
14         {
15             ans += 1
16         }
17         else
18         {
19             var set:Set<Int> = Set<Int>()
20             for i in k..<n
21             {
22                 if (k == 0 || sq(A[k - 1] + A[i])) && !set.contains(A[i])
23                 {
24                     set.insert(A[i])
25                     swap(&A, k, i)
26                     dfs(&A, k + 1)
27                     swap(&A, k, i)
28                 }
29             }
30         }
31     }
32     
33     func sq(_ n:Int) -> Bool
34     {
35         var r = Int(sqrt(Double(n)))
36         return r * r == n
37     }
38     
39     func swap(_ A:inout [Int],_ i:Int,_ j:Int)
40     {
41         var temp:Int = A[i]
42         A[i] = A[j]
43         A[j] = temp        
44     }
45 }

     Runtime: 12 ms

    Memory Usage: 19.1 MB
     1 class Solution {
 2     var ans:Int = 0
 3     func numSquarefulPerms(_ A: [Int]) -> Int {
 4         var A = A
 5         ans = 0
 6         dfs(&A,0)
 7         return ans        
 8     }
 9     
10     func dfs(_ A:inout [Int],_ k:Int)
11     {
12         var n:Int = A.count
13         if k == n
14         {
15             ans += 1
16         }
17         else
18         {
19             var set:Set<Int> = Set<Int>()
20             for i in k..<n
21             {
22                 if (k == 0 || sq(A[k - 1] + A[i])) && !set.contains(A[i])
23                 {
24                     set.insert(A[i])
25                     A.swapAt(k, i)
26                     dfs(&A, k + 1)
27                     A.swapAt(k, i)
28                 }
29             }
30         }
31     }
32     
33     func sq(_ n:Int) -> Bool
34     {
35         var r = Int(sqrt(Double(n)))
36         return r * r == n
37     }
38 }
    12ms
     1 class Solution {
 2     func numSquarefulPerms(_ A: [Int]) -> Int {
 3         var dict = [Int: Set<Int>]()
 4         for (i1, num1) in A.enumerated() {
 5             for (i2, num2) in A.enumerated() where i2 != i1 {
 6                 if matches(num1, num2) {
 7                     dict[num1, default: []].insert(num2)
 8                 }
 9             }
10         }
11         
12         var count = 0
13         fillData([], dict, A, &count)
14         
15         return count
16     }
17     
18     func fillData(_ array: [Int], _ dict: [Int: Set<Int>], _ ref: [Int], _ count: inout Int) {
19         if ref.count == 0 {
20             count += 1
21             return
22         }
23         
24         let targetNums: Set<Int>
25         if array.count == 0 {
26             targetNums = Set(ref)
27         } else {
28             targetNums = dict[array.last!] ?? []
29         }
30         
31         for targetNum in targetNums {
32             if let i = ref.index(of: targetNum) {
33                 var nextRef = ref
34                 var nextArray = [nextRef.remove(at: i)]
35                 fillData(nextArray, dict, nextRef, &count)
36             }
37         }
38     }
39     
40     func matches(_ num1: Int, _ num2: Int) -> Bool {
41         let sqrted = Int(sqrt(Double(num1 + num2)))
42         return sqrted * sqrted == num1 + num2
43     }
44 }
     1 class Solution {
 2     var cache: [Int: Bool] = [0:true]    
 3     func numSquarefulPerms(_ A: [Int]) -> Int {
 4         cache = [0:true]
 5         
 6         var helpMap: [[Int]: [Int:Bool]] = [:]
 7         var helpMap1: [[Int]: [Int:Bool]] = [:]
 8         for i in (0..<A.count) {
 9             guard helpMap[[A[i]]] == nil else { continue }
10             var vv = (helpMap[[A[i]]] ?? [:])
11             vv[i] = true
12             helpMap[[A[i]]] = vv
13         }
14         for place in (1..<A.count) {
15             for i in (0..<A.count) {
16                 for (key, value) in helpMap {
17                     guard value[i] == nil else { continue }
18                     if helpMap1[key + [A[i]]] == nil, comp(key.last! + A[i]) {
19                         var vv = value
20                         vv[i] = true
21                         helpMap1[key + [A[i]]] = vv
22                     }
23                 }
24             }
25             helpMap = helpMap1
26             helpMap1 = [:]
27         }
28         return helpMap.keys.count
29     }
30         
31     func comp(_ val: Int) -> Bool {
32             if let res = cache[val] { return res }
33             let sq = Double(val).squareRoot()
34             if Double(Int(sq)) == sq {
35                 cache[val] = true
36                 return true
37             } else {
38                 cache[val] = false
39                 return false
40             } 
41         return false
42     }
43 }
     1 class Solution {
 2     var cache: [Int: Bool] = [0:true]
 3     func permute(items: [Int]) -> [[Int]] {
 4         // This is a scratch space for Heap's algorithm
 5         var scratch = Array(items)
 6         // This will accumulate our result
 7         var result: [[Int]] = [] 
 8         var endPerm: [[Int]: Bool] = [:]
 9         
10         var allP = 0
11         var allowedP = 0
12         
13         func heap(_ n: Int) {
14             let ar = Array(scratch[n..<scratch.count])
15             if n < scratch.count, endPerm[ar] != nil { return }
16             endPerm[ar] = true
17             allP += 1
18              allowedP += 1
19            if n == 1 {
20                if checkAr(scratch) {
21                    result.append(scratch)
22                }
23                endPerm[scratch] = true
24                return
25             }
26 
27             for i in 0..<n-1 {
28                 heap(n-1)               
29                 let j = (n%2 == 1) ? 0 : i
30                 scratch.swapAt(j, n-1)   
31             }            
32              heap(n-1)
33         }
34 
35         // Let's get started
36         heap(scratch.count)
37         print(allP, allowedP)
38         // And return the result we built up
39         return result
40     }
41     
42     func numSquarefulPerms(_ A: [Int]) -> Int {
43         cache = [0:true]
44        
45         var helpMap: [[Int]: [Int:Bool]] = [:]
46         var helpMap1: [[Int]: [Int:Bool]] = [:]
47         for i in (0..<A.count) {
48             guard helpMap[[A[i]]] == nil else { continue }
49             var vv = (helpMap[[A[i]]] ?? [:])
50             vv[i] = true
51             helpMap[[A[i]]] = vv
52         }
53          print(helpMap)
54         for place in (1..<A.count) {
55             for i in (0..<A.count) {
56                 for (key, value) in helpMap {
57                     guard value[i] == nil else { continue }
58                     if helpMap1[key + [A[i]]] == nil, comp(key.last! + A[i]) {
59                         var vv = value
60                         vv[i] = true
61                         helpMap1[key + [A[i]]] = vv
62                     }
63                 }
64             }
65             helpMap = helpMap1
66             helpMap1 = [:]
67         }
68                 
69         return helpMap.keys.count
70     }
71     
72     func checkAr(_ A: [Int]) -> Bool {
73         for i in (1..<A.count) {
74             let val = A[i-1] + A[i]
75             if !comp(val) { return false }
76         }
77         return true
78     }
79     
80     func comp(_ val: Int) -> Bool {
81             if let res = cache[val] { return res }
82             let sq = Double(val).squareRoot()
83             if Double(Int(sq)) == sq {
84                 cache[val] = true
85                 return true
86             } else {
87                 cache[val] = false
88                 return false
89             } 
90         return false
91     }
92 }
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  • 原文地址：https://www.cnblogs.com/strengthen/p/10390780.html
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