Today I have done leetcode's April LeetCoding Challenge with cpp.

April LeetCoding Challenge 6

Description

Minimum Remove to Make Valid Parentheses

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.

Constraints:

• 1 <= s.length <= 105
• s[i] is either'(' , ')', or lowercase English letter.

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
  string removeOne(const string &s, char front, char back) {
    string result;
    int count = 0;
    for(auto c : s) {
      if(c == front) {
        count += 1;
        result.push_back(front);
      } else if(c == back) {
        if(!count) continue;
        count -= 1;
        result.push_back(back);
      } else {
        result.push_back(c);
      }
    }
    return result;
  }
public:
  string minRemoveToMakeValid(string s) {
    int count = 0;
    string answer = removeOne(s, '(', ')');
    reverse(answer.begin(), answer.end());
    answer = removeOne(answer, ')', '(');
    reverse(answer.begin(), answer.end());
    return answer;
  }
};