[Swift]LeetCode1249. 移除无效的括号 | Minimum Remove to Make Valid Parentheses

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Given a string s of '(' , ')' and lowercase English characters. 

Your task is to remove the minimum number of parentheses ( '(' or ')', in any positions ) so that the resulting parentheses string is valid and return any valid string.

Formally, a parentheses string is valid if and only if:

It is the empty string, contains only lowercase characters, or
It can be written as AB (A concatenated with B), where A and B are valid strings, or
It can be written as (A), where A is a valid string.

Example 1:

Input: s = "lee(t(c)o)de)"
Output: "lee(t(c)o)de"
Explanation: "lee(t(co)de)" , "lee(t(c)ode)" would also be accepted.
Example 2:

Input: s = "a)b(c)d"
Output: "ab(c)d"
Example 3:

Input: s = "))(("
Output: ""
Explanation: An empty string is also valid.
Example 4:

Input: s = "(a(b(c)d)"
Output: "a(b(c)d)"

Constraints:

1 <= s.length <= 10^5
s[i] is one of  '(' , ')' and lowercase English letters.

---

给你一个由 '('、')' 和小写字母组成的字符串 s。

你需要从字符串中删除最少数目的 '(' 或者 ')' （可以删除任意位置的括号)，使得剩下的「括号字符串」有效。

请返回任意一个合法字符串。

有效「括号字符串」应当符合以下 任意一条 要求：

空字符串或只包含小写字母的字符串
可以被写作 AB（A 连接 B）的字符串，其中 A 和 B 都是有效「括号字符串」
可以被写作 (A) 的字符串，其中 A 是一个有效的「括号字符串」

示例 1：

输入：s = "lee(t(c)o)de)"
输出："lee(t(c)o)de"
解释："lee(t(co)de)" , "lee(t(c)ode)" 也是一个可行答案。
示例 2：

输入：s = "a)b(c)d"
输出："ab(c)d"
示例 3：

输入：s = "))(("
输出：""
解释：空字符串也是有效的
示例 4：

输入：s = "(a(b(c)d)"
输出："a(b(c)d)"

提示：

1 <= s.length <= 10^5
s[i] 可能是 '('、')' 或英文小写字母

---

188ms

class Solution {
    func minRemoveToMakeValid(_ s: String) -> String {
        var parentheses = Array<Int>()
        var deleteIndex = [Int]()
        var chars = [Character](s)
        for i in 0..<s.count {
            if chars[i] == "(" {
                parentheses.append(i)
            } else if chars[i] == ")" {
                if parentheses.isEmpty {
                    deleteIndex.append(i)
                } else {
                    parentheses.removeLast()
                }
            }
        }
        deleteIndex.append(contentsOf: parentheses)
        let sortedIndex = deleteIndex.sorted { $0 > $1}
        for index in sortedIndex {
            chars.remove(at: index)
        }
        return String(chars)
    }
}

---

192ms

class Solution {
    func minRemoveToMakeValid(_ s: String) -> String {
        var leftParentheses = Array<Int>()
        var charsLeft = Array<Bool>(repeating: true, count: s.count)
        var chars = [Character](s)
        for i in 0..<s.count {
            if chars[i] == "(" {
                leftParentheses.append(i)
            } else if chars[i] == ")" {
                if leftParentheses.isEmpty {
                    charsLeft[i]  = false
                } else {
                    leftParentheses.popLast()
                }
            }
        }
        for i in 0..<leftParentheses.count {
            charsLeft[leftParentheses[i]] = false
        }

        var  ans = ""
        for i in 0..<chars.count {
            if charsLeft[i] {
                ans.append(chars[i])
            }
        }
        return ans
    }
}

---

240ms

class Solution {
    func minRemoveToMakeValid(_ s: String) -> String {
        var opens = 0
        var result = [Character]()
        
        for char in s {
            if char != "(" && char != ")" {
                result.append(char)
            } else if char == ")" {
                if opens > 0 {
                    result.append(char)
                    opens -= 1
                }
            } else {
                opens += 1
                result.append(char)
            }
        }
        
        if opens == 0 {
            return String(result)
        }
        
        var realResult = [Character]()
        
        for char in result.reversed() {
            if char == "(" && opens > 0 {
                opens -= 1
                continue
            } else {
                realResult.append(char)
            }
        }
        return String(realResult.reversed())
    }
}

---

Runtime: 256 ms

Memory Usage: 25.7 MB

class Solution {
    func minRemoveToMakeValid(_ s: String) -> String {
        var arrS:[Character] = Array(s)
        var stack:[Int] = [Int]()
        for i in 0..<arrS.count
        {
            if arrS[i] == "(" {stack.append(i)}
            if arrS[i] == ")"
            {
                if !stack.isEmpty {stack.removeLast()}
                else
                {
                    arrS[i] = "*"
                }
            }
        }
        while(!stack.isEmpty)
        {
            arrS[stack.removeLast()] = "*"
        }
        return String(arrS.filter{$0 != "*"})
    }
}