Given a string S of '(' and ')' parentheses, we add the minimum number of parentheses ( '(' or ')', and in any positions ) so that the resulting parentheses string is valid.
Formally, a parentheses string is valid if and only if:
- It is the empty string, or
- It can be written as
AB(Aconcatenated withB), whereAandBare valid strings, or - It can be written as
(A), whereAis a valid string.
Given a parentheses string, return the minimum number of parentheses we must add to make the resulting string valid.
Example 1:
Input: "())" Output: 1
Example 2:
Input: "(((" Output: 3
Example 3:
Input: "()" Output: 0
Example 4:
Input: "()))((" Output: 4
Note:
S.length <= 1000Sonly consists of'('and')'characters.
Solution: Counting
Time complexity: O(n)
Space complexity: O(1)
C++
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// Author: Huahua class Solution { public: int minAddToMakeValid(string S) { int l = 0; int m = 0; for (char c : S) { if (c == '(') ++l; if (c == ')' && l > 0) { --l; ++m; } } return S.size() - m * 2; } }; |
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