removeOutermostParens.js

// 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:
// S.length <= 10000
// S[i] is "(" or ")"
// S is a valid parentheses string


const test1 = "(()())(())";
const test2 = "(()())(())(()(()))";
const test3 = "()()";

const removeOuterParenthesis = (s) => {
    let counter = 0;
    let str = "";
    for (const char of s) {
        if (char === "(" && counter > 0) {
            console.log("before add char", char, counter);
            str += char;
            counter++;
            console.log("added char", str, counter);
        }
        if (char === ")" && counter > 1) {
            console.log('before add char',char,  counter);
            str += char;
            counter--;
            console.log("added char", str, counter);
        }
        if (char === "(") {
            counter++;
        } else {
            counter--;
        }
    }
    console.log("final counter", counter);
    return str;
}

console.log(removeOuterParenthesis(test1)); // "()()()"
// console.log(removeOuterParenthesis(test2)); // "()()()()(())"
// console.log(removeOuterParenthesis(test3));  // ""