题解 | #44.有效括号序列#

碰到[ { (入栈

碰到] } )弹出栈顶做比较，不匹配直接返回false

注意循环遍历完后需要再次判断stack.length是否为0

function isValid( s ) {
  let stack = []; 
  for(let i=0; i<s.length; i++){
    if(s[i]=='(' || s[i]=='{' || s[i]=='[')
      stack.push(s[i]);
    else
      if( s[i]==')' && stack.pop()=='(' ||
          s[i]=='}' && stack.pop()=='{' ||
          s[i]==']' && stack.pop()=='['  )
        continue;
      else
        return false;
  }
  if(stack.length!=0)
    return false;
  return true;
}
module.exports = {
    isValid : isValid
};