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 withB
), whereA
andB
are valid strings, or - It can be written as
(A)
, whereA
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.
Solution: Couting
Count how many “(” are open and how many “)” left.
Time complexity: O(n)
Space complexity: O(1)
C++
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// Author: Huahua class Solution { public: string minRemoveToMakeValid(string s) { int close = count(begin(s), end(s), ')'); int open = 0; string ans; for (char c : s) { if (c == '(') { if (open == close) continue; ++open; } else if (c == ')') { --close; if (open == 0) continue; --open; } ans += c; } return ans; } }; |