Minimum Add to Make Parentheses Valid

[fkdl0048]

class Solution {
public:
    int minAddToMakeValid(string s) {
        int open = 0, close = 0;

        for (int i = 0; i < s.size(); i++) {
            if (s[i] == '(')
                open++;
            else {
                close++;
                if (open > 0) {
                    open--;
                    close--;
                }
            }
        }

        return open + close;
    }
};

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