[Swift]LeetCode508. 出現次數最多的子樹元素和 | Most Frequent Subtree Sum

時間 2019-11-11

標籤 swift leetcode508 leetcode 出現次數最多元素 frequent subtree sum 欄目 Swift 简体版

原文原文鏈接

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➤微信公衆號：山青詠芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
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Given the root of a tree, you are asked to find the most frequent subtree sum. The subtree sum of a node is defined as the sum of all the node values formed by the subtree rooted at that node (including the node itself). So what is the most frequent subtree sum value? If there is a tie, return all the values with the highest frequency in any order.node

Examples 1
Input:git

  5
 /  \
2   -3

return [2, -3, 4], since all the values happen only once, return all of them in any order. github

Examples 2
Input:微信

  5
 /  \
2   -5

return [2], since 2 happens twice, however -5 only occur once. app

Note: You may assume the sum of values in any subtree is in the range of 32-bit signed integer.post

給出二叉樹的根，找出出現次數最多的子樹元素和。一個結點的子樹元素和定義爲以該結點爲根的二叉樹上全部結點的元素之和（包括結點自己）。而後求出出現次數最多的子樹元素和。若是有多個元素出現的次數相同，返回全部出現次數最多的元素（不限順序）。 spa

示例 1
輸入:code

  5
 /  \
2   -3

返回 [2, -3, 4]，全部的值均只出現一次，以任意順序返回全部值。orm

示例 2
輸入:

  5
 /  \
2   -5

返回 [2]，只有 2 出現兩次，-5 只出現 1 次。

提示：假設任意子樹元素和都可以用 32 位有符號整數表示。

Runtime: 64 ms

Memory Usage: 21.2 MB

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
16         var res:[Int] = [Int]()
17         var m:[Int:Int] = [Int:Int]()
18         var cnt:Int = 0
19         postorder(root, &m, &cnt)
20         for (key,val) in m
21         {
22             if val == cnt 
23             {
24                 res.append(key)
25             }
26         }
27         return res
28     }
29     
30     func postorder(_ node: TreeNode?,_ m:inout [Int:Int],_ cnt:inout Int) -> Int
31     {
32         if node == nil {return 0}
33         var left:Int = postorder(node!.left, &m, &cnt)
34         var right:Int = postorder(node!.right, &m, &cnt)
35         var sum = left + right + node!.val
36         if m[sum] == nil
37         {
38             m[sum] = 1
39         }
40         else
41         {
42             m[sum]! += 1
43         }        
44         cnt = max(cnt, m[sum]!)
45         return sum
46     }
47 }

64ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
16         var result = [Int:Int]()
17         _ = _findFrequentTreeSum(root, &result)
18         
19         let maxRepeat = result.values.max() ?? 0
20         
21         return result.compactMap { key,value in
22             guard value == maxRepeat else { return nil }
23             return key
24         }
25     }
26     
27     func _findFrequentTreeSum(_ root: TreeNode?, 
28                               _ result: inout [Int:Int]) -> Int 
29     {
30         guard let root = root else { return 0 }
31         
32         var value = root.val
33         value += _findFrequentTreeSum(root.left, &result)
34         value += _findFrequentTreeSum(root.right, &result)
35         
36         result[value] = (result[value] ?? 0) + 1
37         
38         return value
39     }
40 }

76ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
16         guard let root = root else { return [] }
17         
18         var counter = [Int : Int]()
19         func dfs(_ node: TreeNode?) -> Int {
20             guard let node = node else { return 0 }
21             let s = node.val + dfs(node.left) + dfs(node.right)
22             counter[s, default: 0] += 1
23             return s
24         }
25         
26         dfs(root)
27         let kvs = counter.sorted(by: {$0.1 > $1.1})
28         let freq = kvs[0].value
29         var ret = [Int]()
30         for (s, f) in kvs {
31             if f == freq {
32                 ret.append(s)
33             }
34         }
35         return ret
36     }
37 }

84ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     var mp = [Int: Int]()
16 
17 func postorder(_ root: TreeNode?) -> Int{
18     if (root == nil) {
19         return 0;
20     }
21     
22     let left = postorder(root?.left);
23     let right = postorder(root?.right);
24     
25     let sum = (root?.val)! + left + right;
26     
27     if mp[sum] != nil {
28         mp[sum]! += 1
29     } else {
30          mp[sum] =  1
31     }
32     return sum;
33 }
34 
35 
36 func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
37     postorder(root)
38     print(mp)
39     var fq = [Int]()
40     var max = Int.min
41     for number in mp.values {
42         if max < number {
43             max = number
44         }
45     }
46     
47     for (i,number) in mp {
48         if max == number {
49             fq.append(i)
50         }
51     }
52     
53    return fq
54   }
55 }

104ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 class Solution {
15     func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
16         var map = [Int: Int]()
17         traverse(root, &map)
18         
19         var result = [Int]()
20         var max = 0
21         for (sum, count) in map {
22             if count == max {
23                 result.append(sum)
24             } else if count > max {
25                 result.removeAll()
26                 max = count
27                 result.append(sum)
28             }
29         }
30         return result
31     }
32     
33     private func traverse(_ node: TreeNode?, _ map: inout [Int: Int]) -> Int {
34         guard let node = node else { return 0 }
35         
36         let sum = node.val + traverse(node.left, &map) + traverse(node.right, &map)
37         map[sum, default: 0] += 1
38         
39         return sum
40     }
41 }

108ms

 1 /**
 2  * Definition for a binary tree node.
 3  * public class TreeNode {
 4  *     public var val: Int
 5  *     public var left: TreeNode?
 6  *     public var right: TreeNode?
 7  *     public init(_ val: Int) {
 8  *         self.val = val
 9  *         self.left = nil
10  *         self.right = nil
11  *     }
12  * }
13  */
14 
15 class Solution {
16     
17     func recordSubTreeSums(_ root: TreeNode?, _ subTreeSumMap: inout Dictionary<Int, Int>) -> Int {
18         
19         guard let node = root else { return 0 }
20         
21         let subTreeSum =    recordSubTreeSums(node.left, &subTreeSumMap) + 
22                             recordSubTreeSums(node.right, &subTreeSumMap) +
23                             node.val
24         
25         if let count = subTreeSumMap[subTreeSum] {
26             subTreeSumMap[subTreeSum] = count + 1
27         } else {
28             subTreeSumMap[subTreeSum] = 1
29         }
30         
31         return subTreeSum
32     }
33     
34     func findFrequentTreeSum(_ root: TreeNode?) -> [Int] {
35         
36         var subTreeSumMap:Dictionary<Int, Int> = [:]
37         var result:[Int] = []
38     
39         recordSubTreeSums(root, &subTreeSumMap)
40         
41         var maxCount = -1
42         
43         for key in subTreeSumMap.keys {
44             if let count = subTreeSumMap[key] {
45                 if (count > maxCount) { maxCount = count }
46             }
47         }
48         
49         for key in subTreeSumMap.keys {
50             if let count = subTreeSumMap[key] {
51                 if (count == maxCount) { result = result + [key] }
52             }
53         }
54         
55         return result
56     }
57 }