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[Swift]LeetCode1021. 删除最外层的括号 | Remove Outermost Parentheses

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A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and +represents string concatenation.  For example, "", "()", "(())()", and "(()(()))" are all valid parentheses strings.

A valid parentheses string S is primitive if it is nonempty, and there does not exist a way to split it into S = A+B, with A and Bnonempty valid parentheses strings.

Given a valid parentheses string S, consider its primitive decomposition: S = P_1 + P_2 + ... + P_k, where P_i are primitive valid parentheses strings.

Return S after removing the outermost parentheses of every primitive string in the primitive decomposition of S.

Example 1:

Input: "(()())(())"
Output: "()()()"
Explanation: 
The input string is "(()())(())", with primitive decomposition "(()())" + "(())".
After removing outer parentheses of each part, this is "()()" + "()" = "()()()".

Example 2:

Input: "(()())(())(()(()))"
Output: "()()()()(())"
Explanation: 
The input string is "(()())(())(()(()))", with primitive decomposition "(()())" + "(())" + "(()(()))".
After removing outer parentheses of each part, this is "()()" + "()" + "()(())" = "()()()()(())".

Example 3:

Input: "()()"
Output: ""
Explanation: 
The input string is "()()", with primitive decomposition "()" + "()".
After removing outer parentheses of each part, this is "" + "" = "". 

Note:

  1. S.length <= 10000
  2. S[i] is "(" or ")"
  3. S is a valid parentheses string

有效括号字符串为空 ("")、"(" + A + ")" 或 A + B，其中 A 和 B 都是有效的括号字符串，+ 代表字符串的连接。例如，""，"()"，"(())()" 和 "(()(()))" 都是有效的括号字符串。

如果有效字符串 S 非空，且不存在将其拆分为 S = A+B 的方法，我们称其为原语（primitive），其中 A 和 B 都是非空有效括号字符串。

给出一个非空有效字符串 S，考虑将其进行原语化分解，使得：S = P_1 + P_2 + ... + P_k，其中 P_i 是有效括号字符串原语。

对 S 进行原语化分解，删除分解中每个原语字符串的最外层括号，返回 S 。

示例 1：

输入："(()())(())"
输出："()()()"
解释：
输入字符串为 "(()())(())"，原语化分解得到 "(()())" + "(())"，
删除每个部分中的最外层括号后得到 "()()" + "()" = "()()()"。

示例 2：

输入："(()())(())(()(()))"
输出："()()()()(())"
解释：
输入字符串为 "(()())(())(()(()))"，原语化分解得到 "(()())" + "(())" + "(()(()))"，
删除每隔部分中的最外层括号后得到 "()()" + "()" + "()(())" = "()()()()(())"。

示例 3：

输入："()()"
输出：""
解释：
输入字符串为 "()()"，原语化分解得到 "()" + "()"，
删除每个部分中的最外层括号后得到 "" + "" = ""。

提示：

  1. S.length <= 10000
  2. S[i] 为 "(" 或 ")"
  3. S 是一个有效括号字符串

24ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         guard !S.isEmpty else { return "" }
 4         var result = [Character]()
 5         var inSub = true, backCount = 0
 6         let s = Array(S)
 7     
 8         for i in 1..<s.count {
 9             if s[i] == "(" {
10                 if inSub {
11                     backCount += 1
12                     result.append("(")
13                 } else {
14                     inSub = true
15                     backCount = 0
16                 }           
17                 continue
18         }
19             
20             if s[i] == ")" {
21                 backCount -= 1                
22                 if backCount == -1 {
23                     inSub = false
24                 } else {
25                     result.append(")")
26                 }
27                 continue
28             }
29         }
30         return String(result)
31      }
32 }

28ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         var chars = Array(S)
 4         var count = 0
 5         var previousCount = 0
 6         var resultArray = [Character]()
 7         
 8         for i in 0..<chars.count {
 9             previousCount = count
10             if chars[i] == "(" {
11                 count += 1
12             } else if chars[i] == ")" {
13                 count -= 1
14             }
15             if count != 0 && previousCount != 0 {
16                 resultArray.append(chars[i])
17             }
18         }
19         let result = String(resultArray)
20         return result
21     }
22 }

32ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String
 3     {
 4         var oc = 0
 5         var temp = ""
 6         var ret = ""
 7         for c in S
 8         {
 9             if c == "(" { oc += 1 }
10             else { oc -= 1 }
11             
12             temp += String(c)
13             if oc == 0 {
14                 ret += self.helper(temp)
15                 temp = ""
16             }
17         }
18         return ret
19     }
20     
21     private func helper(_ S: String) -> String
22     {
23         guard S.count > 0 else { return S }
24         
25         var ret = S
26         if let idx = ret.index(of: "(") { ret.remove(at: idx) }
27         if let idx = ret.lastIndex(of: ")") { ret.remove(at: idx) }
28         return ret
29     }
30 }

36ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         var s = S.characters.map{String($0)}
 4         var temp = [String]()
 5         var hold = ""
 6         var openCount = 0
 7         var closeCount = 0
 8         var i = 0
 9         while i < s.count{
10             if s[i] == "("{
11                 hold += s[i]
12                 openCount += 1
13             }else if hold.count != 0 && s[i] == ")"{
14                 hold += ")"
15                 closeCount += 1
16             }
17             if hold.count != 0 && closeCount == openCount{
18                 temp.append(hold)
19                 openCount = 0
20                 closeCount = 0
21                 hold = ""
22             }
23             i += 1
24         }
25         
26         var answer = ""
27         for pair in temp{
28                 let startIndex  = pair.index(pair.startIndex, offsetBy: 1)
29                 let endIndex = pair.index(pair.endIndex, offsetBy: -1)
30                 answer += String(pair[startIndex..<endIndex])
31         }
32         
33         return answer
34     }
35 }

Runtime: 40 ms

Memory Usage: 19.5 MB
 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         var ret:String = String()
 4         var bal:Int = 0
 5         var cur:String = String()
 6         for c in S
 7         {
 8             if c == "("
 9             {
10                 bal += 1
11             }
12             else
13             {
14                 bal -= 1
15             }
16             cur.append(c)
17             if bal == 0
18             {
19                 ret += cur.subString(1, cur.count - 2)
20                 cur = String()
21             }
22         }
23         return ret    
24     }
25 }
26 
27 extension String {
28     // 截取字符串：指定索引和字符数
29     // - begin: 开始截取处索引
30     // - count: 截取的字符数量
31     func subString(_ begin:Int,_ count:Int) -> String {
32         let start = self.index(self.startIndex, offsetBy: max(0, begin))
33         let end = self.index(self.startIndex, offsetBy:  min(self.count, begin + count))
34         return String(self[start..<end]) 
35     }  
36 }

48ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         if S.count == 0 {
 4             return ""
 5         }
 6         var s = Array(S)
 7         var sk = [Character]()
 8         var otherSk = [Character]()
 9         var anOtherSK = [Character]()
10         while s.isEmpty == false {
11             if sk.isEmpty {
12                 if anOtherSK.isEmpty {
13                     anOtherSK.append(s.removeLast())
14                 } else {
15                     if s.last == "(" {
16                         s.popLast()
17                         anOtherSK.popLast()
18                         continue
19                     }
20                 }
21             }
22             if sk.isEmpty && s.last == "(" {
23                 continue
24             }
25             
26             if let a = s.popLast() {
27                 sk.append(a)
28                 otherSk.append(a)
29             }
30             if sk.last == "(" {
31                 sk.popLast()
32                 sk.popLast()
33             }
34         }
35         return String(otherSk.reversed())
36     }
37 }

52ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3         let S = Array(S)
 4         var stack: [Character] = []
 5         var res: [String] = []
 6         var prev = 0
 7         for (i, ch) in S.enumerated() {
 8             if ch == "(" || ch == "[" || ch == "{" {
 9                stack.append(ch) 
10             }
11             
12             if ch == ")" || ch == "}"  || ch == "]"  {
13                 stack.remove(at: stack.count - 1)
14             }
15             
16             if stack.count == 0 {
17                res.append(String(S[prev...i]))
18                 prev = i + 1
19             }
20         }
21     
22         return res.reduce("", {res, str in return res + String(String(str.dropFirst()).dropLast())})
23     }
24 }

72ms

 1 class Solution {
 2     func removeOuterParentheses(_ S: String) -> String {
 3     let parentheses = Array(S)
 4     var groups = [[String]]()
 5     let stack = Stack<String>()
 6     var startIndex = 0
 7     var result = ""
 8     for (index, parenthese) in parentheses.enumerated() {
 9       if stack.isEmpty() && index == 0 {
10         stack.push(String(parenthese))
11       } else {
12         if let element = stack.top?.element, element != String(parenthese) {
13           stack.pop()
14         } else {
15           stack.push(String(parenthese))
16         }
17       }
18       if stack.isEmpty() {
19         groups.append(Array(parentheses[startIndex...index]).map{ String($0) })
20         startIndex = index + 1
21       }
22     }
23     
24     for group in groups {
25       let simplified = Array(group.dropFirst().dropLast())
26       result += simplified.joined()
27     }
28     
29     return result
30   }
31 }
32 
33 final class Stack<Element> {
34   
35   var top: Node<Element>?
36   
37   @discardableResult
38   func pop() -> Element? {
39     guard let topNode = top else { return nil }
40     top = topNode.next
41     return topNode.element
42   }
43   
44   func push(_ element: Element) {
45     if let topNode = top {
46       let newTop = Node(element)
47       newTop.next = topNode
48       top = newTop
49     } else {
50       top = Node(element)
51     }
52   }
53   
54   func isEmpty() -> Bool {
55     return top == nil
56   }
57 }
58 
59 extension Stack {
60   
61   final class Node<Element> {
62     
63     var element: Element?
64     var next: Node<Element>?
65     
66     init(_ element: Element) {
67       self.element = element
68     }
69   }
70 }

 

posted @ 2019-04-07 22:57  为敢技术  阅读(736)  评论(0)  编辑  收藏  举报