0020-valid-parentheses.js

/**
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/valid-parentheses/
 * @param {string} s
 * @return {boolean}
 */
 var isValid = (s, stack = []) => {
    for (const bracket of s.split('')) {/* Time O(N) */
        const isParenthesis = bracket === '(';
        if (isParenthesis) stack.push(')');  /* Space O(N) */

        const isCurlyBrace = bracket === '{';
        if (isCurlyBrace) stack.push('}');   /* Space O(N) */

        const isSquareBracket = bracket === '[';
        if (isSquareBracket) stack.push(']');/* Space O(N) */

        const isOpenPair = isParenthesis || isCurlyBrace || isSquareBracket;
        if (isOpenPair) continue;

        const isEmpty = !stack.length;
        const isWrongPair = stack.pop() !== bracket;
        const isInvalid = isEmpty || isWrongPair;
        if (isInvalid) return false;
    }

    return (stack.length === 0);
};

/**
 * Time O(N) | Space O(N)
 * https://leetcode.com/problems/valid-parentheses/
 * @param {string} s
 * @return {boolean}
 */
var isValid = (s, stack = []) => {
    const map = {
        '}': '{',
        ']': '[',
        ')': '(',
    };
    
    for (const char of s) {/* Time O(N) */
        const isBracket = (char in map)
        if (!isBracket) { stack.push(char); continue; }/* Space O(N) */

        const isEqual = (stack[stack.length - 1] === map[char])
        if (isEqual) { stack.pop(); continue; }

        return false;
    }

    return (stack.length === 0);
};