[Swift]LeetCode472. 鏈接詞 | Concatenated Words

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Given a list of words (without duplicates), please write a program that returns all concatenated words in the given list of words.

A concatenated word is defined as a string that is comprised entirely of at least two shorter words in the given array.

Example:

Input: ["cat","cats","catsdogcats","dog","dogcatsdog","hippopotamuses","rat","ratcatdogcat"]

Output: ["catsdogcats","dogcatsdog","ratcatdogcat"]

Explanation: "catsdogcats" can be concatenated by "cats", "dog" and "cats"; 
 "dogcatsdog" can be concatenated by "dog", "cats" and "dog"; 
"ratcatdogcat" can be concatenated by "rat", "cat", "dog" and "cat". 

Note:

1. The number of elements of the given array will not exceed 10,000
2. The length sum of elements in the given array will not exceed 600,000.
3. All the input string will only include lower case letters.
4. The returned elements order does not matter.

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給定一個不含重複單詞的列表，編寫一個程序，返回給定單詞列表中全部的鏈接詞。

鏈接詞的定義爲：一個字符串徹底是由至少兩個給定數組中的單詞組成的。

示例:

輸入: ["cat","cats","catsdogcats","dog","dogcatsdog","hippopotamuses","rat","ratcatdogcat"]

輸出: ["catsdogcats","dogcatsdog","ratcatdogcat"]

解釋: "catsdogcats"由"cats", "dog" 和 "cats"組成; 
     "dogcatsdog"由"dog", "cats"和"dog"組成; 
     "ratcatdogcat"由"rat", "cat", "dog"和"cat"組成。

說明:

1. 給定數組的元素總數不超過 10000。
2. 給定數組中元素的長度總和不超過 600000。
3. 全部輸入字符串只包含小寫字母。
4. 不須要考慮答案輸出的順序。

---

Runtime: 8332 ms

Memory Usage: 10.2 MB

 1 class Solution {
 2     func findAllConcatenatedWordsInADict(_ words: [String]) -> [String] {
 3         var res:[String] = [String]()
 4         var dict:Set<String> = Set(words)
 5         for word in words
 6         {
 7             var n:Int = word.count
 8             if n == 0 {continue}
 9             var dp:[Bool] = [Bool](repeating:false,count:n + 1)
10             dp[0] = true
11             for i in 0..<n
12             {
13                 if !dp[i] {continue}
14                 for j in (i + 1)...n
15                 {
16                     var str:String = word.subString(i, j - i)
17                     if j - i < n && dict.contains(str)
18                     {
19                         dp[j] = true
20                     }
21                 }
22                 if dp[n] 
23                 {
24                     res.append(word)
25                     break
26                 }
27             }
28         }
29         return res
30     }
31 }
32 
33 extension String {
34     // 截取字符串：指定索引和字符數
35     // - begin: 開始截取處索引
36     // - count: 截取的字符數量
37     func subString(_ begin:Int,_ count:Int) -> String {
38         let start = self.index(self.startIndex, offsetBy: max(0, begin))
39         let end = self.index(self.startIndex, offsetBy:  min(self.count, begin + count))
40         return String(self[start..<end]) 
41     }
42 }