1021. Remove Outermost Parentheses

A valid parentheses string is either empty (""), "(" + A + ")", or A + B, where A and B are valid parentheses strings, and + represents string concatenation.  For example, "", "()", "(())()", and "(()(()))" are all valid parentheses strings.

A valid parentheses string S is primitive if it is nonempty, and there does not exist a way to split it into S = A+B, with A and B nonempty valid parentheses strings.

Given a valid parentheses string S, consider its primitive decomposition: S = P_1 + P_2 + ... + P_k, where P_i are primitive valid parentheses strings.

Return S after removing the outermost parentheses of every primitive string in the primitive decomposition of S.

 

Example 1:

Input: "(()())(())"
Output: "()()()"
Explanation: 
The input string is "(()())(())", with primitive decomposition "(()())" + "(())".
After removing outer parentheses of each part, this is "()()" + "()" = "()()()".

Example 2:

Input: "(()())(())(()(()))"
Output: "()()()()(())"
Explanation: 
The input string is "(()())(())(()(()))", with primitive decomposition "(()())" + "(())" + "(()(()))".
After removing outer parentheses of each part, this is "()()" + "()" + "()(())" = "()()()()(())".

Example 3:

Input: "()()"
Output: ""
Explanation: 
The input string is "()()", with primitive decomposition "()" + "()".
After removing outer parentheses of each part, this is "" + "" = "".

 

Note:

  1. S.length <= 10000
  2. S[i] is "(" or ")"
  3. S is a valid parentheses string
 

Rust Solution

struct Solution;

impl Solution {
    fn remove_outer_parentheses(s: String) -> String {
        let mut res: String = "".to_string();
        let mut count = 0;
        for c in s.chars() {
            if c == '(' {
                count += 1;
                if count > 1 {
                    res.push(c);
                }
            } else {
                count -= 1;
                if count != 0 {
                    res.push(c);
                }
            }
        }
        res
    }
}

#[test]
fn test() {
    let s = "(()())(())".to_string();
    let t = "()()()".to_string();
    assert_eq!(Solution::remove_outer_parentheses(s), t);
    let s = "(()())(())(()(()))".to_string();
    let t = "()()()()(())".to_string();
    assert_eq!(Solution::remove_outer_parentheses(s), t);
    let s = "()()".to_string();
    let t = "".to_string();
    assert_eq!(Solution::remove_outer_parentheses(s), t);
}

Having problems with this solution? Click here to submit an issue on github.