[Swift]LeetCode521. 最長特殊序列 Ⅰ | Longest Uncommon Subsequence I

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Given a group of two strings, you need to find the longest uncommon subsequence of this group of two strings. The longest uncommon subsequence is defined as the longest subsequence of one of these strings and this subsequence should not be any subsequence of the other strings.

A subsequence is a sequence that can be derived from one sequence by deleting some characters without changing the order of the remaining elements. Trivially, any string is a subsequence of itself and an empty string is a subsequence of any string.

The input will be two strings, and the output needs to be the length of the longest uncommon subsequence. If the longest uncommon subsequence doesn't exist, return -1.

Example 1:

Input: "aba", "cdc"
Output: 3
Explanation: The longest uncommon subsequence is "aba" (or "cdc"), 
because "aba" is a subsequence of "aba", 
but not a subsequence of any other strings in the group of two strings. 

 Note:

1. Both strings' lengths will not exceed 100.
2. Only letters from a ~ z will appear in input strings.

---

 

給定兩個字符串，你須要從這兩個字符串中找出最長的特殊序列。最長特殊序列定義以下：該序列爲某字符串獨有的最長子序列（即不能是其餘字符串的子序列）。

子序列能夠經過刪去字符串中的某些字符實現，但不能改變剩餘字符的相對順序。空序列爲全部字符串的子序列，任何字符串爲其自身的子序列。

輸入爲兩個字符串，輸出最長特殊序列的長度。若是不存在，則返回 -1。

示例 :

輸入: "aba", "cdc"
輸出: 3
解析: 最長特殊序列可爲 "aba" (或 "cdc")

說明:

1. 兩個字符串長度均小於100。
2. 字符串中的字符僅含有 'a'~'z'。

---

8ms

 1 class Solution {
 2     func findLUSlength(_ a: String, _ b: String) -> Int {
 3         //每一個字符串的最長子序列爲其自己
 4         //最長特殊序列的長度一定爲a.count 或者b.count或者-1,三者居其一。
 5         if a == b {return -1}
 6         else if a.count == b.count {return a.count}
 7         else
 8         {
 9             return max(a.count,b.count)
10         }
11     }
12 }

---

8ms

 1 import Foundation
 2 
 3 class Solution {
 4     func findLUSlength(_ a: String, _ b: String) -> Int {
 5         if (a == b) {
 6             return -1
 7         } else {
 8             return max(a.count,b.count)
 9         }
10     }
11 }

---

12ms

 1 class Solution {
 2     func findLUSlength(_ a: String, _ b: String) -> Int {
 3         let m = a.count
 4         let n = b.count
 5         
 6         if a == b {
 7             return -1
 8         }else if m > n {
 9             return m
10         }else{
11             return n
12         }
13     }
14 }

---

16ms

 1 class Solution {
 2     func findLUSlength(_ a: String, _ b: String) -> Int {
 3         guard a != b else {
 4             return -1
 5         }
 6         if a.count == 0 {
 7             return b.count
 8         }
 9         if b.count == 1 {
10             return a.count
11         }
12         let longer = a.count > b.count ? Array(a) : Array(b)
13         let shorter = a.count > b.count ? Array(b) : Array(a)
14         var count = 0
15         var start = 0
16         var end = longer.count
17         while start < end {
18             while end > start {
19                 if (String(shorter).range(of: String(longer[start..<end])) == nil) {
20                     count = max(longer[start..<end].count, count)
21                 }
22                 end -= 1
23             }
24             start += 1
25         }
26         return count
27     }
28 }