Interviews

Brackets from Bolt.js

/*
'(', '{', '[' are called "openers".
')', '}', ']' are called "closers".
Write an efficient function that tells us whether input string's openers
and closers are properly nested.


Examples:
"{ [ ] ( ) }" -> true
"{ [ ( ] ) }" -> false
"{ [ }" -> false
"class Example { public do() { return; } }" -> true
"class Example { public do( { return; } }" -> false

"<>"
"''"
"||"

*/
const SIMILAR_BRACKETS = {
    "'": "'",
    "|": "|",
}
const BRACKETS = {
    '{': '}',
    '[': ']',
    '(': ')',
    '<': '>'
}
const MIRRORED_BRACKETS = Object.keys(BRACKETS).reduce((acc, el) => {
    acc[BRACKETS[el]] = el;
    return acc;
}, {});

function solution(value) {
    const stack = [];
    const similarBracketsCounter = {};

    for (let i = 0; i < value.length; i++) {
        const char = value[i];
        if (!BRACKETS[char] && !MIRRORED_BRACKETS[char] && !SIMILAR_BRACKETS[char]) {
            continue;
        }
        if (BRACKETS[char]) {
            // opener
            stack.push(char);
        } else if (MIRRORED_BRACKETS[char]) {
            // closer
            const lastOpener = stack[stack.length - 1];
            if (lastOpener !== MIRRORED_BRACKETS[char]) {
                return false;
            }
            stack.pop();
        } else if (SIMILAR_BRACKETS[char]) {
            similarBracketsCounter[char] = similarBracketsCounter[char] || 0;
            similarBracketsCounter[char]++;

            const isCloser = (
                similarBracketsCounter[char] % 2 === 0 &&
                stack[stack.length - 1] === char
            );
            if (isCloser) {
                stack.pop();
            } else {
                stack.push(char);
            }
        }
    }
    return (
        stack.length === 0 &&
        Object.values(similarBracketsCounter).every((el) => el % 2 === 0)
    );
}

function test(value, expectedResult) {
    const realResult = solution(value);
    console.log(realResult === expectedResult, `${value} expected to give ${expectedResult}`);
}

test('', true);
test('some', true);
test('(', false);
test('()', true);
test('()[', false);
test('()[]', true);
test(')', false);
test('([)]', false);
test('((', false);
test('())', false);
//
test('class Example { public do() { return; } }', true);
test('class Example { public do( { return; } }', false);

test("('['", false); 
test("(')'", false);
test('("("[]")")', true);
test("(')'", false);
test("'||'''", true)