LeetCode 1021. Remove Outermost Parentheses

Problem Statement

impl Solution {
    pub fn remove_outer_parentheses(s: String) -> String {
        let (mut ans, mut open) = ("".to_string(), 0);
        for c in s.chars() {
            if c == '(' {
                if open > 0 {
                    ans.push(c);
                }
                open += 1;
            }
            if c == ')'{
                if open > 1 {
                    ans.push(c);
                }
                open -= 1;
            }
        }
        return ans;
    }
}