Valid Parentheses

Description

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

An input string is valid if:

1. Open brackets must be closed by the same type of brackets.
2. Open brackets must be closed in the correct order.

 

Example 1:

Input: s = "()"
Output: true

Example 2:

Input: s = "()[]{}"
Output: true

Example 3:

Input: s = "(]"
Output: false

Example 4:

Input: s = "([)]"
Output: false

Example 5:

Input: s = "{[]}"
Output: true

 

Constraints:

• 1 <= s.length <= 104
• s consists of parentheses only '()[]{}'.

Solution(javascript)

/**
 * @param {string} s
 * @return {boolean}
 */
const isValid = function (s) {
  const stack = []
  const pair = {
    '[': ']',
    '{': '}',
    '(': ')',
  }
  const isPaired = (a, b) => pair[a] === b

  for (c of s) {
    if (isPaired(stack[stack.length - 1], c)) {
      stack.pop()
    } else {
      stack.push(c)
    }
  }
  return stack.length === 0
}