20. Valid Parentheses

/* Given a string containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

An input string is valid if:

Open brackets must be closed by the same type of brackets.
Open brackets must be closed in the correct order.
Note that an empty string is also considered valid.

Example 1:

Input: "()"
Output: true
Example 2:

Input: "()[]{}"
Output: true
Example 3:

Input: "(]"
Output: false
Example 4:

Input: "([)]"
Output: false
Example 5:

Input: "{[]}"
Output: true */

/**
 * @param {string} s
 * @return {boolean}
 */

//Time = O(n), Sapce = O(n)
var isValid = function (s) {
	const bracketHash = {
			'{': '}',
			'[': ']',
			'(': ')',
		},
		stack = [],
		len = s.length

	for (let i = 0; i < len; i++) {
		const char = s[i]
		if (bracketHash.hasOwnProperty(char)) {
			stack.push(char)
		} else if (bracketHash[stack.pop()] !== char) return false
	}
	return !stack.length //return true returns true for array of length 1
}

//Test cases
console.log(isValid('()[]{}'))
console.log(isValid('['))