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

parentheses.js

/**
 * question : 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.
 */
let parenthese = "()[]{}"
function checkByReplace(s) {
  while(true) {
    let len = s.length;
    // Replace the string with '' one by one according to the matching pair
    s =  s.replace('()', '').replace('[]', '').replace('{}', '');
    /**
     * two case when s.length equal to len
     * 1. when all parentheses are matched and s become ''.
     * 2. s cannot continue to match and its length is the same as the begining
     *  means ([) is length is 3 after replace it is still 3 so return false.
     * in both case we have same length
     */
    if(s.length === len) {
      return len === 0;
    }
  }
}

function checkByStack(s) {
  if(!s) return true; // empty character string is valid.
  const leftToRight = {
    '(' : ')',
    '{' : '}',
    '[' : ']'
  };
  const stack = [];
  for(let i = 0, len = s.length; i < len; i++) {
    const ch = s[i];
    // if left parentheses then push to stack.
    if(leftToRight[ch]) {
      stack.push(ch);
    } else {
        /**
         * start to match parentheses
         * if no left parentheses in stack means return false.
         * if data but top element of stack is not the current colosing parentheses then return false.
         */
      if(!stack.length || (leftToRight[stack.pop()] !== ch)) {
        return false;
      }
    }
  }
  return !stack.length;
}
console.time('checkByReplace');
console.log('checkByReplace', checkByReplace(parenthese));
console.timeEnd('checkByReplace');

console.time('checkByStack');
console.log('checkByStack', checkByStack(parenthese))
console.timeEnd('checkByStack');