Remove Outermost Parentheses

Remove Outermost Parentheses - LeetCode

INTRODUCTION

Given a valid parentheses string s, Return s after removing the outermost parentheses of every primitive string in the primitive decomposition of s.

Example 1:

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

Example 2:

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

Example 3:

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

APPROACH

We are going to use java’s StringBuilder to build string as we iterate through the input string of s.

Next, for each iteration, we’ll append to the output variable based on these conditions.

1. if (c == '(' && count++ > 0) output.append(c);
2. if (c == ')' && count-- > 1) output.append(c);

Finally, we will output the built string with output.toString();

SOLUTION

class Solution {
  public String removeOuterParentheses(String s) {
      StringBuilder output = new StringBuilder();
      int count = 0;

      for(char c : s.toCharArray()){
        if (c == '(' && count++ > 0) output.append(c);      
        if (c == ')' && count-- > 1) output.append(c);
      }
      return output.toString();
  }
}