[Swift]LeetCode678. 有效的括号字符串 | Valid Parenthesis String

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Given a string containing only three types of characters: '(', ')' and '*', write a function to check whether this string is valid. We define the validity of a string by these rules:

1. Any left parenthesis '(' must have a corresponding right parenthesis ')'.
2. Any right parenthesis ')' must have a corresponding left parenthesis '('.
3. Left parenthesis '(' must go before the corresponding right parenthesis ')'.
4. '*' could be treated as a single right parenthesis ')' or a single left parenthesis '(' or an empty string.
5. An empty string is also valid. 

Example 1:

Input: "()"
Output: True 

Example 2:

Input: "(*)"
Output: True 

Example 3:

Input: "(*))"
Output: True 

Note:

1. The string size will be in the range [1, 100].

---

给定一个只包含三种字符的字符串：（ ，） 和 *，写一个函数来检验这个字符串是否为有效字符串。有效字符串具有如下规则：

1. 任何左括号 ( 必须有相应的右括号 )。
2. 任何右括号 ) 必须有相应的左括号 ( 。
3. 左括号 ( 必须在对应的右括号之前 )。
4. * 可以被视为单个右括号 ) ，或单个左括号 ( ，或一个空字符串。
5. 一个空字符串也被视为有效字符串。

示例 1:

输入: "()"
输出: True

示例 2:

输入: "(*)"
输出: True

示例 3:

输入: "(*))"
输出: True

注意:

1. 字符串大小将在 [1，100] 范围内。

---

4ms

class Solution {
    func checkValidString(_ s: String) -> Bool {
        let left = Character("(")
        let right = Character(")")
        let anyMatch = Character("*")
        var minLeft = 0
        var maxLeft = 0
        for char in s {
            if char == left {
                minLeft += 1
                maxLeft += 1
            } else if char == right {
                minLeft -= 1
                maxLeft -= 1
            } else if char == anyMatch {
                minLeft -= 1
                maxLeft += 1
            }
            minLeft = max(0, minLeft)
            if maxLeft < 0 {
                return false
            }
        }
        return minLeft == 0
    }
}

---

8ms

class Solution {
    func checkValidString(_ s: String) -> Bool {
        let left = Character("(")
        let right = Character(")")
        let anyMatch = Character("*")
        var count = 0
        for char in s {
            if char == right {
                count -= 1
            } else {
                count += 1
            }
            if count < 0 {
                return false
            }
        }
        count = 0
        for char in s.reversed() {
            if char == left {
                count -= 1
            } else {
                count += 1
            }
            if count < 0 {
                return false
            }
        }
        return true
    }
}

---

Runtime: 12 ms

Memory Usage: 19.7 MB

class Solution {
    func checkValidString(_ s: String) -> Bool {
        var arr:[Character] = Array(s)
        var left:[Int] = [Int]()
        var star:[Int] = [Int]()
        for i in 0..<arr.count
        {
            if arr[i] == "*"
            {
                star.append(i)
            }
            else if arr[i] == "("
            {
                left.append(i)
            }
            else
            {
                if left.isEmpty && star.isEmpty 
                {
                    return false
                }
                if !left.isEmpty 
                {
                    left.removeLast()
                }
                else 
                {
                    star.removeLast()
                }
            }            
        }
        while(!left.isEmpty && !star.isEmpty)
        {
            if left.last! > star.last!
            {
                return false
            }
            left.removeLast()
            star.removeLast()
        }
        return left.isEmpty
    }
}

---

16ms

class Solution {
    func checkValidString(_ s: String) -> Bool {
        let left = Character("(")
        let right = Character(")")
        let anyMatch = Character("*")
        var leftStack = [Int]()
        var anyMatchStack = [Int]()
        for (i, char) in s.enumerated() {
            if char == right {
                if let top = leftStack.last {
                    leftStack.popLast()
                } else if let top = anyMatchStack.last {
                    anyMatchStack.popLast()
                } else {
                    return false
                }
            } else if char == left {
                leftStack.append(i)
            } else if char == anyMatch {
                anyMatchStack.append(i)
            }
        }
        var leftIndex = leftStack.count - 1
        var anyMatchIndex = anyMatchStack.count - 1
        while leftIndex >= 0 && anyMatchIndex >= 0 {
            if leftStack[leftIndex] > anyMatchStack[anyMatchIndex] {
                return false
            }
            leftIndex -= 1
            anyMatchIndex -= 1
        }
        return leftIndex < 0
    }
}

---

260ms

class Solution {
    func checkValidString(_ s: String) -> Bool {
         let str = Array(s)
        var memo = [[Int]].init(repeating: [Int].init(repeating: -1, count: s.count), count: s.count)
        
        func isValid(_ l: Int, _ r: Int) -> Int {
            guard l <= r else {
                return 1
            }
            guard memo[l][r] == -1 else {
                return memo[l][r]
            }
            if l == r && str[l] == "*" {
                memo[l][r] = 1
                return 1
            }
            
            if (str[l] == "(" || str[l] == "*") && (str[r] == ")" || str[r] == "*") && isValid(l+1, r-1) == 1 {
                memo[l][r] = 1
                return 1
            }
            
            for k in l ..< r {
                if isValid(l, k) == 1 && isValid(k+1, r) == 1 {
                    memo[l][r] = 1
                    return 1
                }
            }
            
            memo[l][r] = 0
            return 0
        }
        
        return isValid(0, s.count - 1) == 1
    }
}