findCorrespondingClosingParentheses.tsx

/**
 * Time complexity: O(6)
 * Space complexity: O(3n) - almost 3x original array size? No entirely sure
 *
 * Assumes that the inputs are valid
 *
 * @param openingParenthesisIndex Zero based index of '(' in str
 * @param str String to search - must be equal # of '(' and ')'
 */
const getCorrespondingClosingParenthesesIndex = (openingParenthesisIndex: number, str: string): number => {
    const start: string = str.substring(0, openingParenthesisIndex + 1) // include openParenthesis index
    const end: string   = str.substr(openingParenthesisIndex + 1, str.length) // exclude openParenthesis index

    const closingParentheses: string[] = end.split(')')


    // how many '(' do we remove from the end to get our matching ')'
    const openingParenthesesCount: number = start.split('(').length - 1

    // remove this many parentheses from the end
    const everythingUpToTarget = closingParentheses.splice(0, closingParentheses.length - openingParenthesesCount)
    
    // put the pieces back, without the unmatched ')'
    const result = (start + everythingUpToTarget.join(')'))

    return result.length
}


console.log(getCorrespondingClosingParenthesesIndex(9, 'a(aa(aaaa(a(a)aa)aaa)aa)a'))