Brace balancing

braceBalancing.ts

const OPEN_BRACES = ['[', '{', '('] as const;
type OpenBrace = typeof OPEN_BRACES[number]

const CLOSED_BRACES = [']', '}', ')'] as const;
type ClosedBrace = typeof CLOSED_BRACES[number];

type AnyBrace = OpenBrace | ClosedBrace;

function isBraceOpen(brace: AnyBrace): brace is OpenBrace {
    return OPEN_BRACES.includes(brace);
}

function isAnyBrace(brace: unknown): brace is AnyBrace {
    return [...OPEN_BRACES, ...CLOSED_BRACES].includes(brace);
}

const MATCHING_BRACES: Record<OpenBrace, ClosedBrace> = {
    "{": "}",
    "[": "]",
    "(": ")",
}

function areBracesBalanced(brances: AnyBrace[]) {
    const stack: OpenBrace[] = [];

    for (let brace of brances) {
        if (isBraceOpen(brace)) {
            stack.push(brace);
        } else {
            const lastBrace = stack.pop();
            const expectedBrace = lastBrace && MATCHING_BRACES[lastBrace];
            if (expectedBrace !== brace) {
                return false;
            }
        }
    }

    if (stack.length === 0) {
        return true;
    }

    return false
}

function areBracesBalancedRec(braces: AnyBrace[], stack: OpenBrace[] = []): boolean {
    const [head, ...tail] = braces;
    if (isBraceOpen(head)) {
        return areBracesBalancedRec(tail, [head, ...stack]);
    }
    const [previousBrace, ...stackRest] = stack;
    if (MATCHING_BRACES[previousBrace] !== head) {
        return false;
    }

    if (tail.length === 0) {
        return true;
    }

    return areBracesBalancedRec(tail, stackRest);;
}

const test = '[]{[()]}{}'.split('')

if (test.every(isAnyBrace)) {
    console.log(areBracesBalancedRec(test))
}