Practice-problems/validParantheses.js at master · jyliu17/Practice-problems · GitHub

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/**
Given a string s 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.


Example 1:

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

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

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

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

**/

var isValid = function(s) {

 if (s.length ==0 || s.length%2 != 0){
        return false;
    }

 const stack = [];
  const closingParen = {
    '(': ')',
    '{': '}',
    '[': ']'
  };
  for (let i = 0; i < s.length; i++) {
    if (s[i] === '(' || s[i] === '{' || s[i] === '[') {
      stack.push(s[i]);
    } else if (closingParen[stack.pop()] !== s[i]) {
      return false;
    }
  }

 return stack.length === 0

 /** return stack.length ? 0 : 1 **/


};