LeetCode-20. Valid Parentheses

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问题描述

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.

Constraints:

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

解答

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/**
 * @param {string} s
 * @return {boolean}
 */
const isValid = function (s) {
  let stack = []
  let dict = {
    '(': ')',
    '[': ']',
    '{': '}'
  }

  for (let i = 0; i < s.length; i++) {
    if (dict[s[i]] !== undefined) {
      stack.push(dict(s[i]))
    } else if (s[i] !== stack.pop()) {
      return false
    }
  }
  return stack.length === 0
}