[Swift]LeetCode677. 键值映射 | Map Sum Pairs

Implement a MapSum class with insert, and sum methods.

For the method insert, you‘ll be given a pair of (string, integer). The string represents the key and the integer represents the value. If the key already existed, then the original key-value pair will be overridden to the new one.

For the method sum, you‘ll be given a string representing the prefix, and you need to return the sum of all the pairs‘ value whose key starts with the prefix.

Example 1:

Input: insert("apple", 3), Output: Null
Input: sum("ap"), Output: 3
Input: insert("app", 2), Output: Null
Input: sum("ap"), Output: 5

对于方法 insert，你将得到一对（字符串，整数）的键值对。字符串表示键，整数表示值。如果键已经存在，那么原来的键值对将被替代成新的键值对。

对于方法 sum，你将得到一个表示前缀的字符串，你需要返回所有以该前缀开头的键的值的总和。

示例 1:

输入: insert("apple", 3), 输出: Null
输入: sum("ap"), 输出: 3
输入: insert("app", 2), 输出: Null
输入: sum("ap"), 输出: 5

Memory Usage: 19.9 MB

 1 class MapSum {
 2     var m:[String:[Int]]
 3
 4     /** Initialize your data structure here. */
 5     init() {
 6         m = [String:[Int]]()
 7     }
 8
 9     func insert(_ key: String, _ val: Int) {
10         var diff:Int = val - m[key,default:[0,0]][0]
11         var n:Int = key.count
12         m[key,default:[0,0]][0] = val
13         for i in stride(from:n - 1,to:0,by:-1)
14         {
15             m[key.subString(0, i),default:[0,0]][1] += diff
16         }
17     }
18
19     func sum(_ prefix: String) -> Int {
20         return m[prefix,default:[0,0]][0] + m[prefix,default:[0,0]][1]
21     }
22 }
23
24 extension String {
25     // 截取字符串：指定索引和字符数
26     // - begin: 开始截取处索引
27     // - count: 截取的字符数量
28     func subString(_ begin:Int,_ count:Int) -> String {
29         let start = self.index(self.startIndex, offsetBy: max(0, begin))
30         let end = self.index(self.startIndex, offsetBy:  min(self.count, begin + count))
31         return String(self[start..<end])
32     }
33 }
34
35 /**
36  * Your MapSum object will be instantiated and called as such:
37  * let obj = MapSum()
38  * obj.insert(key, val)
39  * let ret_2: Int = obj.sum(prefix)
40  */ 

 1 class MapSum {
 2     private let root = TrieNode()
 3
 4     /** Initialize your data structure here. */
 5     init() {
 6
 7     }
 8
 9     func insert(_ key: String, _ val: Int) {
10         var node = root
11         for c in key {
12             let next = node.insert(c, val)
13             node = next
14         }
15         node.sum = val
16     }
17
18     func sum(_ prefix: String) -> Int {
19         var node = root
20         for c in prefix {
21             guard let next = node.search(c) else {
22                 return 0
23             }
24             node = next
25         }
26         return node.allSum()
27     }
28 }
29
30 class TrieNode {
31
32     var sum = 0
33     private var map = [Character: TrieNode]()
34
35     func insert(_ c: Character, _ val: Int) -> TrieNode {
36         if let node = map[c] {
37             return node
38         }
39         let node = TrieNode()
40         map[c] = node
41         return node
42     }
43
44     func search(_ c: Character) -> TrieNode? {
45         return map[c]
46     }
47
48     func allSum() -> Int {
49         var val = sum
50         map.forEach {
51             val += $1.allSum()
52         }
53         return val
54     }
55 }

 1 class Node {
 2     var value: Character?
 3     var parent: Node?
 4     var children: [Character : Node] = [:]
 5     var sum: Int?
 6
 7     init(value: Character? = nil, parent: Node? = nil) {
 8         self.value = value
 9         self.parent = parent
10     }
11
12     func add(letter: Character) {
13         guard children[letter] == nil else { return }
14         children[letter] = Node(value: letter, parent: self)
15     }
16 }
17
18 class MapSum {
19     let root = Node()
20
21     init() {
22
23     }
24
25     func insert(_ key: String, _ val: Int) {
26         guard !key.isEmpty else { return }
27         var currentNode = root
28
29         for char in key {
30             currentNode.add(letter: char)
31             guard let node = currentNode.children[char] else { continue }
32             currentNode = node
33         }
34
35         currentNode.sum = val
36     }
37
38     func sum(_ prefix: String) -> Int {
39         guard !prefix.isEmpty else { return 0 }
40         var currentNode = root
41
42         for char in prefix {
43             if let node = currentNode.children[char] {
44                 currentNode = node
45             } else {
46                 return 0
47             }
48         }
49
50         return findWords(node: currentNode)
51     }
52
53     func findWords(node: Node) -> Int {
54         var result = 0
55
56         for child in node.children {
57             result +=  findWords(node: child.value)
58         }
59
60         return result + (node.sum ?? 0)
61     }
62 }

原文地址：https://www.cnblogs.com/strengthen/p/10498122.html