367. Valid Perfect Square

/*Given a positive integer num, write a function which returns True if num is a perfect square else False.Note: Do not use any built-in library function such as sqrt.Example 1:Input: 16Returns: TrueExample 2:Input: 14Returns: False*///思路，开方之后，判断是否是整数即（int）(num)==num;//62.5%  0msbool isPerfectSquare(int num) {    if((int)(sqrt(num))==sqrt(num))        return true;    else        return false;}