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➤微信公众号：山青咏芝（shanqingyongzhi）
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➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址：https://www.cnblogs.com/strengthen/p/10241414.html
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Remove the minimum number of invalid parentheses in order to make the input string valid. Return all possible results.
Note: The input string may contain letters other than the parentheses ( and ).
Example 1:
Input: "()())()" Output: ["()()()", "(())()"]
Example 2:
Input: "(a)())()" Output: ["(a)()()", "(a())()"]
Example 3:
Input: ")("
Output: [""]
删除最小数量的无效括号，使得输入的字符串有效，返回所有可能的结果。
说明: 输入可能包含了除 ( 和 ) 以外的字符。
示例 1:
输入: "()())()" 输出: ["()()()", "(())()"]
示例 2:
输入: "(a)())()" 输出: ["(a)()()", "(a())()"]
示例 3:
输入: ")("
输出: [""]
20ms
1 class Solution { 2 func removeInvalidParentheses(_ s: String) -> [String] { 3 var paths = [String]() 4 dfs(&paths, Array(s), 0, 0, ("(", ")")) 5 return paths 6 } 7 8 fileprivate func dfs(_ paths: inout [String], _ s: [Character], _ lastValid: Int, _ lastRight: Int, _ parens: (Character, Character)) { 9 var count = 0, s = s 10 11 for i in lastValid ..< s.count { 12 if s[i] == parens.0 { 13 count += 1 14 } 15 16 if s[i] == parens.1 { 17 count -= 1 18 } 19 20 if count < 0 { 21 for j in lastRight ... i { 22 guard s[j] == parens.1 else { 23 continue 24 } 25 26 guard j == 0 || s[j] != s[j - 1] || j == lastRight else { 27 continue 28 } 29 30 dfs(&paths, Array(s[0 ..< j] + s[j + 1 ..< s.count]), i, j, parens) 31 } 32 return 33 } 34 } 35 36 if parens.0 == "(" { 37 dfs(&paths, s.reversed(), 0, 0, (")", "(")) 38 } else { 39 paths.append(String(s.reversed())) 40 } 41 } 42 }
40ms
1 class Solution { 2 func removeInvalidParentheses(_ s: String) -> [String] { 3 4 var res = [String]() 5 var repeated = Set<String>() 6 removeRight(s, &res, &repeated) 7 return res 8 } 9 10 func removeRight(_ s : String, _ res : inout [String], _ repeated : inout Set<String>) { 11 let sArr = Array(s) 12 var count = 0 13 for i in 0..<sArr.count { 14 let c = sArr[i] 15 if c == "(" { 16 count += 1 17 }else if c == ")" { 18 count -= 1 19 } 20 21 if count < 0 { 22 for j in 0...i where sArr[j] == ")" { 23 let r = String(sArr[0..<j] + sArr[j+1..<sArr.count]) 24 if repeated.contains(r) { 25 continue 26 } 27 repeated.insert(r) 28 removeRight(r, &res, &repeated) 29 } 30 return 31 } 32 } 33 if count == 0 { 34 res.append(s) 35 return 36 } 37 38 removeLeft(s, &res, &repeated) 39 } 40 41 func removeLeft(_ s : String, _ res : inout [String], _ repeated : inout Set<String>) { 42 let sArr = Array(s) 43 var count = 0 44 for i in stride(from: sArr.count-1, to: -1, by: -1) { 45 let c = sArr[i] 46 if c == ")" { 47 count += 1 48 }else if c == "("{ 49 count -= 1 50 } 51 52 if count < 0 { 53 for j in stride(from: sArr.count-1, to: i-1, by: -1) where sArr[j] == "(" { 54 let r = String(sArr[0..<j] + sArr[j+1..<sArr.count]) 55 if repeated.contains(r) { 56 continue 57 } 58 repeated.insert(r) 59 removeLeft(r, &res, &repeated) 60 } 61 return 62 } 63 } 64 res.append(s) 65 } 66 }
84ms
1 class Solution { 2 func isValid(_ str:String) -> Bool { 3 4 var left = 0 5 6 for char in str { 7 8 if char == Character("(") { 9 10 left += 1 11 } 12 13 if char == Character(")") { 14 15 left -= 1 16 } 17 18 if left < 0 { 19 20 return false 21 } 22 } 23 24 return left == 0 25 } 26 27 func removeInvalidParentheses(_ s: String) -> [String] { 28 29 var results:[String] = [] 30 31 if isValid(s) { 32 33 return [s] 34 } 35 36 let mustRemove = findInvalid(s) 37 38 removeAndCheck(s, start:0, left: mustRemove.left, right: mustRemove.right, &results) 39 40 return results 41 } 42 43 func removeAndCheck(_ str:String, start:Int, left:Int, right:Int, _ results:inout [String]) { 44 45 if left == 0 && right == 0 { 46 47 if isValid(str) { 48 49 results.append(str) 50 } 51 52 return 53 } 54 55 for i in start..<str.count { 56 57 let index = str.index(str.startIndex, offsetBy: i) 58 59 let next = str.index(after: index) 60 61 if i != start { 62 63 let prev = str.index(before: index) 64 65 if str[index] == str[prev] { 66 67 continue 68 } 69 } 70 71 let char = str[index] 72 73 if char == Character("(") && left > 0 { 74 75 let substr = String(str[str.startIndex..<index] + str[next...]) 76 77 removeAndCheck(substr, start:i, left: left - 1, right: right , &results) 78 } 79 80 if char == Character(")") && right > 0 { 81 82 let substr = String(str[str.startIndex..<index] + str[next...]) 83 84 removeAndCheck(substr, start:i, left: left, right: right - 1, &results) 85 } 86 } 87 } 88 89 func findInvalid(_ str:String) -> (left:Int, right:Int) { 90 91 var cnt1 = 0, cnt2 = 0 92 93 for char in str { 94 95 if char == Character("(") { 96 97 cnt1 += 1 98 } 99 100 if cnt1 == 0 { 101 102 if char == Character(")") { 103 104 cnt2 += 1 105 } 106 } 107 else { 108 109 if char == Character(")") { 110 111 cnt1 -= 1 112 } 113 } 114 } 115 116 return (cnt1, cnt2) 117 } 118 }
672ms
1 class Solution { 2 func removeInvalidParentheses(_ s: String) -> [String] { 3 var result = [String]() 4 var queue = [String]() 5 var isFound = false 6 var set = Set<String>() 7 8 queue.append(s) 9 10 while !queue.isEmpty && !isFound { 11 let size = queue.count 12 for _ in 0..<size { 13 let s1 = queue.removeFirst() 14 if isValid(s1) { 15 result.append(String(s1)) 16 isFound = true 17 } 18 19 if !isFound { 20 let chars = Array(s1) 21 for i in 0..<s1.count { 22 23 if chars[i] != "(" && chars[i] != ")" { 24 continue 25 } 26 27 if i > 0 && chars[i] == chars[i - 1] { 28 continue 29 } 30 31 var newChars = chars 32 newChars.remove(at: i) 33 let s2 = String(newChars) 34 if !set.contains(s2) { 35 queue.append(s2) 36 set.insert(s2) 37 } 38 } 39 } 40 } 41 } 42 43 return result 44 } 45 46 func isValid(_ s: String) -> Bool { 47 if s.isEmpty { return true } 48 var count = 0 49 for c in s { 50 if c == "(" { 51 count += 1 52 } else if c == ")" { 53 count -= 1 54 if count < 0 { 55 return false 56 } 57 } 58 } 59 return count == 0 60 } 61 }
1196ms
1 class Solution { 2 let openers: Set<Character> = ["{", "[", "("] 3 let closers: [Character: Character] = ["}":"{", ")": "(", "]": "["] 4 5 func isCorrectlyParenthesized(_ s: String, 6 visited: inout Set<String>, 7 potentialSolutions: inout Set<String>, 8 maxLength: inout Int) -> Bool { 9 if visited.contains(s) { 10 return potentialSolutions.contains(s) 11 } 12 else { 13 visited.insert(s) 14 } 15 if s.count < maxLength { 16 return false 17 } 18 19 guard let first = s.first else { 20 return true 21 } 22 var stack: [(char: Character, index: Int)] = (openers.contains(first) || closers[first] != nil) ? [(char: first, index: 0)] : [] 23 var removedFromStack: [(char: Character, index: Int)] = [] 24 25 var str = s.dropFirst() 26 var i = 0 27 var failed = false 28 while !str.isEmpty { 29 let firstChar = str.removeFirst() 30 i += 1 31 32 if openers.contains(firstChar) { 33 stack.append((char: firstChar, index: i)) 34 continue 35 } 36 37 guard closers[firstChar] != nil else { 38 continue // it's OK to contain other characters. 39 } 40 41 let stackLast = stack.isEmpty ? nil : stack.removeLast() 42 if let stackLast = stackLast { removedFromStack.append(stackLast) } 43 44 if let stackLast = stackLast, closers[firstChar] != stackLast.char { 45 failed = true 46 break 47 } 48 else if stackLast == nil { 49 failed = true 50 break 51 } 52 } 53 54 if !failed, stack.isEmpty, str.isEmpty { 55 let strlen = s.count 56 if maxLength <= strlen, !potentialSolutions.contains(s) { 57 potentialSolutions.insert(s) 58 maxLength = strlen 59 } 60 return true 61 } 62 if s.count >= 1 { 63 for substr in substringsWithParenthesisRemoved(from: s, earliestIndex: 0) { 64 isCorrectlyParenthesized(substr, visited: &visited, potentialSolutions: &potentialSolutions, maxLength: &maxLength) 65 } 66 } 67 return false 68 } 69 70 func substringsWithParenthesisRemoved(from str: String, earliestIndex: Int) -> [String] { 71 var out = [String]() 72 var i = str.index(str.startIndex, offsetBy: earliestIndex) 73 while i != str.endIndex { 74 let charI = str[i] 75 guard openers.contains(charI) || closers[charI] != nil else { 76 i = str.index(after: i) 77 continue 78 } 79 var outstr = str 80 outstr.remove(at: i) 81 out.append(outstr) 82 i = str.index(after: i) 83 } 84 return out 85 } 86 87 func removeInvalidParentheses(_ s: String) -> [String] { 88 var potentialSolutions: Set<String> = [] 89 var visited: Set<String> = [] 90 var maxLen: Int = 0 91 isCorrectlyParenthesized(s, visited: &visited, potentialSolutions: &potentialSolutions, maxLength: &maxLen) ? potentialSolutions : [] 92 let out = Array(potentialSolutions).filter { $0.count == maxLen } 93 return out.count > 0 ? out : [""] 94 } 95 }